GLib.Variant

Fields

None

Methods

class

is_object_path (string)

class

is_signature (string)

class

new_array (child_type, children)

class

new_boolean (value)

class

new_byte (value)

class

new_bytestring (string)

class

new_bytestring_array (strv)

class

new_dict_entry (key, value)

class

new_double (value)

class

new_fixed_array (element_type, elements, n_elements, element_size)

class

new_from_bytes (type, bytes, trusted)

class

new_from_data (type, data, trusted, notify, user_data)

class

new_handle (value)

class

new_int16 (value)

class

new_int32 (value)

class

new_int64 (value)

class

new_maybe (child_type, child)

class

new_object_path (object_path)

class

new_objv (strv)

class

new_signature (signature)

class

new_string (string)

class

new_strv (strv)

class

new_tuple (children)

class

new_uint16 (value)

class

new_uint32 (value)

class

new_uint64 (value)

class

new_variant (value)

class

parse (type, text, limit, endptr)

class

parse_error_print_context (error, source_str)

class

parse_error_quark ()

class

parser_get_error_quark ()

class

split_signature (signature)

byteswap ()

check_format_string (format_string, copy_only)

classify ()

compare (two)

dup_bytestring ()

dup_bytestring_array ()

dup_objv ()

dup_string ()

dup_strv ()

equal (two)

get_boolean ()

get_byte ()

get_bytestring ()

get_bytestring_array ()

get_child_value (index_)

get_data ()

get_data_as_bytes ()

get_double ()

get_handle ()

get_int16 ()

get_int32 ()

get_int64 ()

get_maybe ()

get_normal_form ()

get_objv ()

get_size ()

get_string ()

get_strv ()

get_type ()

get_type_string ()

get_uint16 ()

get_uint32 ()

get_uint64 ()

get_variant ()

hash ()

is_container ()

is_floating ()

is_normal_form ()

is_of_type (type)

keys ()

lookup_value (key, expected_type)

n_children ()

print_ (type_annotate)

ref ()

ref_sink ()

store (data)

take_ref ()

unpack ()

unref ()

Details

class GLib.Variant(format_string, value)

GLib.Variant is a variant datatype; it can contain one or more values along with information about the type of the values.

A GLib.Variant may contain simple types, like an integer, or a boolean value; or complex types, like an array of two strings, or a dictionary of key value pairs. A GLib.Variant is also immutable: once it’s been created neither its type nor its content can be modified further.

GLib.Variant is useful whenever data needs to be serialized, for example when sending method parameters in D-Bus, or when saving settings using GSettings.

When creating a new GLib.Variant, you pass the data you want to store in it along with a string representing the type of data you wish to pass to it.

For instance, if you want to create a GLib.Variant holding an integer value you can use:

GVariant *v = g_variant_new ("u", 40);

The string “u” in the first argument tells GLib.Variant that the data passed to the constructor (40) is going to be an unsigned integer.

More advanced examples of GLib.Variant in use can be found in documentation for GVariant format strings.

The range of possible values is determined by the type.

The type system used by GLib.Variant is GLib.VariantType.

GLib.Variant instances always have a type and a value (which are given at construction time). The type and value of a GLib.Variant instance can never change other than by the GLib.Variant itself being destroyed. A GLib.Variant cannot contain a pointer.

GLib.Variant is reference counted using GLib.Variant.ref() and GLib.Variant.unref(). GLib.Variant also has floating reference counts – see GLib.Variant.ref_sink().

GLib.Variant is completely threadsafe. A GLib.Variant instance can be concurrently accessed in any way from any number of threads without problems.

GLib.Variant is heavily optimised for dealing with data in serialized form. It works particularly well with data located in memory-mapped files. It can perform nearly all deserialization operations in a small constant time, usually touching only a single memory page. Serialized GLib.Variant data can also be sent over the network.

GLib.Variant is largely compatible with D-Bus. Almost all types of GLib.Variant instances can be sent over D-Bus. See GLib.VariantType for exceptions. (However, GLib.Variant's serialization format is not the same as the serialization format of a D-Bus message body: use #GDBusMessage, in the gio library, for those.)

For space-efficiency, the GLib.Variant serialization format does not automatically include the variant’s length, type or endianness, which must either be implied from context (such as knowledge that a particular file format always contains a little-endian %G_VARIANT_TYPE_VARIANT which occupies the whole length of the file) or supplied out-of-band (for instance, a length, type and/or endianness indicator could be placed at the beginning of a file, network message or network stream).

A GLib.Variant's size is limited mainly by any lower level operating system constraints, such as the number of bits in #gsize. For example, it is reasonable to have a 2GB file mapped into memory with GLib.MappedFile, and call GLib.Variant.new_from_data() on it.

For convenience to C programmers, GLib.Variant features powerful varargs-based value construction and destruction. This feature is designed to be embedded in other libraries.

There is a Python-inspired text language for describing GLib.Variant values. GLib.Variant includes a printer for this language and a parser with type inferencing.

Memory Use

GLib.Variant tries to be quite efficient with respect to memory use. This section gives a rough idea of how much memory is used by the current implementation. The information here is subject to change in the future.

The memory allocated by GLib.Variant can be grouped into 4 broad purposes: memory for serialized data, memory for the type information cache, buffer management memory and memory for the GLib.Variant structure itself.

Serialized Data Memory

This is the memory that is used for storing GLib.Variant data in serialized form. This is what would be sent over the network or what would end up on disk, not counting any indicator of the endianness, or of the length or type of the top-level variant.

The amount of memory required to store a boolean is 1 byte. 16, 32 and 64 bit integers and double precision floating point numbers use their “natural” size. Strings (including object path and signature strings) are stored with a nul terminator, and as such use the length of the string plus 1 byte.

Maybe types use no space at all to represent the null value and use the same amount of space (sometimes plus one byte) as the equivalent non-maybe-typed value to represent the non-null case.

Arrays use the amount of space required to store each of their members, concatenated. Additionally, if the items stored in an array are not of a fixed-size (ie: strings, other arrays, etc) then an additional framing offset is stored for each item. The size of this offset is either 1, 2 or 4 bytes depending on the overall size of the container. Additionally, extra padding bytes are added as required for alignment of child values.

Tuples (including dictionary entries) use the amount of space required to store each of their members, concatenated, plus one framing offset (as per arrays) for each non-fixed-sized item in the tuple, except for the last one. Additionally, extra padding bytes are added as required for alignment of child values.

Variants use the same amount of space as the item inside of the variant, plus 1 byte, plus the length of the type string for the item inside the variant.

As an example, consider a dictionary mapping strings to variants. In the case that the dictionary is empty, 0 bytes are required for the serialization.

If we add an item “width” that maps to the int32 value of 500 then we will use 4 byte to store the int32 (so 6 for the variant containing it) and 6 bytes for the string. The variant must be aligned to 8 after the 6 bytes of the string, so that’s 2 extra bytes. 6 (string) + 2 (padding) + 6 (variant) is 14 bytes used for the dictionary entry. An additional 1 byte is added to the array as a framing offset making a total of 15 bytes.

If we add another entry, “title” that maps to a nullable string that happens to have a value of null, then we use 0 bytes for the null value (and 3 bytes for the variant to contain it along with its type string) plus 6 bytes for the string. Again, we need 2 padding bytes. That makes a total of 6 + 2 + 3 = 11 bytes.

We now require extra padding between the two items in the array. After the 14 bytes of the first item, that’s 2 bytes required. We now require 2 framing offsets for an extra two bytes. 14 + 2 + 11 + 2 = 29 bytes to encode the entire two-item dictionary.

Type Information Cache

For each GLib.Variant type that currently exists in the program a type information structure is kept in the type information cache. The type information structure is required for rapid deserialization.

Continuing with the above example, if a GLib.Variant exists with the type “a{sv}” then a type information struct will exist for “a{sv}”, “{sv}”, “s”, and “v”. Multiple uses of the same type will share the same type information. Additionally, all single-digit types are stored in read-only static memory and do not contribute to the writable memory footprint of a program using GLib.Variant.

Aside from the type information structures stored in read-only memory, there are two forms of type information. One is used for container types where there is a single element type: arrays and maybe types. The other is used for container types where there are multiple element types: tuples and dictionary entries.

Array type info structures are 6 * sizeof (void *), plus the memory required to store the type string itself. This means that on 32-bit systems, the cache entry for “a{sv}” would require 30 bytes of memory (plus malloc overhead).

Tuple type info structures are 6 * sizeof (void *), plus 4 * sizeof (void *) for each item in the tuple, plus the memory required to store the type string itself. A 2-item tuple, for example, would have a type information structure that consumed writable memory in the size of 14 * sizeof (void *) (plus type string) This means that on 32-bit systems, the cache entry for “{sv}” would require 61 bytes of memory (plus malloc overhead).

This means that in total, for our “a{sv}” example, 91 bytes of type information would be allocated.

The type information cache, additionally, uses a GLib.HashTable to store and look up the cached items and stores a pointer to this hash table in static storage. The hash table is freed when there are zero items in the type cache.

Although these sizes may seem large it is important to remember that a program will probably only have a very small number of different types of values in it and that only one type information structure is required for many different values of the same type.

Buffer Management Memory

GLib.Variant uses an internal buffer management structure to deal with the various different possible sources of serialized data that it uses. The buffer is responsible for ensuring that the correct call is made when the data is no longer in use by GLib.Variant. This may involve a GLib.free() or a g_slice_free() or even GLib.MappedFile.unref().

One buffer management structure is used for each chunk of serialized data. The size of the buffer management structure is 4 * (void *). On 32-bit systems, that’s 16 bytes.

GLib.Variant structure

The size of a GLib.Variant structure is 6 * (void *). On 32-bit systems, that’s 24 bytes.

GLib.Variant structures only exist if they are explicitly created with API calls. For example, if a GLib.Variant is constructed out of serialized data for the example given above (with the dictionary) then although there are 9 individual values that comprise the entire dictionary (two keys, two values, two variants containing the values, two dictionary entries, plus the dictionary itself), only 1 GLib.Variant instance exists – the one referring to the dictionary.

If calls are made to start accessing the other values then GLib.Variant instances will exist for those values only for as long as they are in use (ie: until you call GLib.Variant.unref()). The type information is shared. The serialized data and the buffer management structure for that serialized data is shared by the child.

Summary

To put the entire example together, for our dictionary mapping strings to variants (with two entries, as given above), we are using 91 bytes of memory for type information, 29 bytes of memory for the serialized data, 16 bytes for buffer management and 24 bytes for the GLib.Variant instance, or a total of 160 bytes, plus malloc overhead. If we were to use GLib.Variant.get_child_value() to access the two dictionary entries, we would use an additional 48 bytes. If we were to have other dictionaries of the same type, we would use more memory for the serialized data and buffer management for those dictionaries, but the type information would be shared.

New in version 2.24.

classmethod is_object_path(string)[source]
Parameters

string (str) – a normal C nul-terminated string

Returns

True if string is a D-Bus object path

Return type

bool

Determines if a given string is a valid D-Bus object path. You should ensure that a string is a valid D-Bus object path before passing it to GLib.Variant.new_object_path().

A valid object path starts with / followed by zero or more sequences of characters separated by / characters. Each sequence must contain only the characters [A-Z][a-z][0-9]_. No sequence (including the one following the final / character) may be empty.

New in version 2.24.

classmethod is_signature(string)[source]
Parameters

string (str) – a normal C nul-terminated string

Returns

True if string is a D-Bus type signature

Return type

bool

Determines if a given string is a valid D-Bus type signature. You should ensure that a string is a valid D-Bus type signature before passing it to GLib.Variant.new_signature().

D-Bus type signatures consist of zero or more definite GLib.VariantType strings in sequence.

New in version 2.24.

classmethod new_array(child_type, children)[source]
Parameters
Returns

a floating reference to a new GLib.Variant array

Return type

GLib.Variant

Creates a new GLib.Variant array from children.

child_type must be non-None if n_children is zero. Otherwise, the child type is determined by inspecting the first element of the children array. If child_type is non-None then it must be a definite type.

The items of the array are taken from the children array. No entry in the children array may be None.

All items in the array must have the same type, which must be the same as child_type, if given.

If the children are floating references (see GLib.Variant.ref_sink()), the new instance takes ownership of them as if via GLib.Variant.ref_sink().

New in version 2.24.

classmethod new_boolean(value)[source]
Parameters

value (bool) – a bool value

Returns

a floating reference to a new boolean GLib.Variant instance

Return type

GLib.Variant

Creates a new boolean GLib.Variant instance – either True or False.

New in version 2.24.

classmethod new_byte(value)[source]
Parameters

value (int) – a #guint8 value

Returns

a floating reference to a new byte GLib.Variant instance

Return type

GLib.Variant

Creates a new byte GLib.Variant instance.

New in version 2.24.

classmethod new_bytestring(string)[source]
Parameters

string (bytes) – a normal nul-terminated string in no particular encoding

Returns

a floating reference to a new bytestring GLib.Variant instance

Return type

GLib.Variant

Creates an array-of-bytes GLib.Variant with the contents of string. This function is just like GLib.Variant.new_string() except that the string need not be valid UTF-8.

The nul terminator character at the end of the string is stored in the array.

New in version 2.26.

classmethod new_bytestring_array(strv)[source]
Parameters

strv ([str]) – an array of strings

Returns

a new floating GLib.Variant instance

Return type

GLib.Variant

Constructs an array of bytestring GLib.Variant from the given array of strings.

If length is -1 then strv is None-terminated.

New in version 2.26.

classmethod new_dict_entry(key, value)[source]
Parameters
Returns

a floating reference to a new dictionary entry GLib.Variant

Return type

GLib.Variant

Creates a new dictionary entry GLib.Variant. key and value must be non-None. key must be a value of a basic type (ie: not a container).

If the key or value are floating references (see GLib.Variant.ref_sink()), the new instance takes ownership of them as if via GLib.Variant.ref_sink().

New in version 2.24.

classmethod new_double(value)[source]
Parameters

value (float) – a float floating point value

Returns

a floating reference to a new double GLib.Variant instance

Return type

GLib.Variant

Creates a new double GLib.Variant instance.

New in version 2.24.

classmethod new_fixed_array(element_type, elements, n_elements, element_size)[source]
Parameters
  • element_type (GLib.VariantType) – the GLib.VariantType of each element

  • elements (object or None) – a pointer to the fixed array of contiguous elements

  • n_elements (int) – the number of elements

  • element_size (int) – the size of each element

Returns

a floating reference to a new array GLib.Variant instance

Return type

GLib.Variant

Constructs a new array GLib.Variant instance, where the elements are of element_type type.

elements must be an array with fixed-sized elements. Numeric types are fixed-size as are tuples containing only other fixed-sized types.

element_size must be the size of a single element in the array. For example, if calling this function for an array of 32-bit integers, you might say sizeof(gint32). This value isn’t used except for the purpose of a double-check that the form of the serialized data matches the caller’s expectation.

n_elements must be the length of the elements array.

New in version 2.32.

classmethod new_from_bytes(type, bytes, trusted)[source]
Parameters
Returns

a new GLib.Variant with a floating reference

Return type

GLib.Variant

Constructs a new serialized-mode GLib.Variant instance. This is the inner interface for creation of new serialized values that gets called from various functions in gvariant.c.

A reference is taken on bytes.

The data in bytes must be aligned appropriately for the type being loaded. Otherwise this function will internally create a copy of the memory (since GLib 2.60) or (in older versions) fail and exit the process.

New in version 2.36.

classmethod new_from_data(type, data, trusted, notify, user_data)[source]
Parameters
Returns

a new floating GLib.Variant of type type

Return type

GLib.Variant

Creates a new GLib.Variant instance from serialized data.

type is the type of GLib.Variant instance that will be constructed. The interpretation of data depends on knowing the type.

data is not modified by this function and must remain valid with an unchanging value until such a time as notify is called with user_data. If the contents of data change before that time then the result is undefined.

If data is trusted to be serialized data in normal form then trusted should be True. This applies to serialized data created within this process or read from a trusted location on the disk (such as a file installed in /usr/lib alongside your application). You should set trusted to False if data is read from the network, a file in the user’s home directory, etc.

If data was not stored in this machine’s native endianness, any multi-byte numeric values in the returned variant will also be in non-native endianness. GLib.Variant.byteswap() can be used to recover the original values.

notify will be called with user_data when data is no longer needed. The exact time of this call is unspecified and might even be before this function returns.

Note: data must be backed by memory that is aligned appropriately for the type being loaded. Otherwise this function will internally create a copy of the memory (since GLib 2.60) or (in older versions) fail and exit the process.

New in version 2.24.

classmethod new_handle(value)[source]
Parameters

value (int) – a #gint32 value

Returns

a floating reference to a new handle GLib.Variant instance

Return type

GLib.Variant

Creates a new handle GLib.Variant instance.

By convention, handles are indexes into an array of file descriptors that are sent alongside a D-Bus message. If you’re not interacting with D-Bus, you probably don’t need them.

New in version 2.24.

classmethod new_int16(value)[source]
Parameters

value (int) – a #gint16 value

Returns

a floating reference to a new int16 GLib.Variant instance

Return type

GLib.Variant

Creates a new int16 GLib.Variant instance.

New in version 2.24.

classmethod new_int32(value)[source]
Parameters

value (int) – a #gint32 value

Returns

a floating reference to a new int32 GLib.Variant instance

Return type

GLib.Variant

Creates a new int32 GLib.Variant instance.

New in version 2.24.

classmethod new_int64(value)[source]
Parameters

value (int) – a #gint64 value

Returns

a floating reference to a new int64 GLib.Variant instance

Return type

GLib.Variant

Creates a new int64 GLib.Variant instance.

New in version 2.24.

classmethod new_maybe(child_type, child)[source]
Parameters
Returns

a floating reference to a new GLib.Variant maybe instance

Return type

GLib.Variant

Depending on if child is None, either wraps child inside of a maybe container or creates a Nothing instance for the given type.

At least one of child_type and child must be non-None. If child_type is non-None then it must be a definite type. If they are both non-None then child_type must be the type of child.

If child is a floating reference (see GLib.Variant.ref_sink()), the new instance takes ownership of child.

New in version 2.24.

classmethod new_object_path(object_path)[source]
Parameters

object_path (str) – a normal C nul-terminated string

Returns

a floating reference to a new object path GLib.Variant instance

Return type

GLib.Variant

Creates a D-Bus object path GLib.Variant with the contents of object_path. object_path must be a valid D-Bus object path. Use GLib.Variant.is_object_path() if you’re not sure.

New in version 2.24.

classmethod new_objv(strv)[source]
Parameters

strv ([str]) – an array of strings

Returns

a new floating GLib.Variant instance

Return type

GLib.Variant

Constructs an array of object paths GLib.Variant from the given array of strings.

Each string must be a valid GLib.Variant object path; see GLib.Variant.is_object_path().

If length is -1 then strv is None-terminated.

New in version 2.30.

classmethod new_signature(signature)[source]
Parameters

signature (str) – a normal C nul-terminated string

Returns

a floating reference to a new signature GLib.Variant instance

Return type

GLib.Variant

Creates a D-Bus type signature GLib.Variant with the contents of string. string must be a valid D-Bus type signature. Use GLib.Variant.is_signature() if you’re not sure.

New in version 2.24.

classmethod new_string(string)[source]
Parameters

string (str) – a normal UTF-8 nul-terminated string

Returns

a floating reference to a new string GLib.Variant instance

Return type

GLib.Variant

Creates a string GLib.Variant with the contents of string.

string must be valid UTF-8, and must not be None. To encode potentially-None strings, use g_variant_new() with ms as the format string.

New in version 2.24.

classmethod new_strv(strv)[source]
Parameters

strv ([str]) – an array of strings

Returns

a new floating GLib.Variant instance

Return type

GLib.Variant

Constructs an array of strings GLib.Variant from the given array of strings.

If length is -1 then strv is None-terminated.

New in version 2.24.

classmethod new_tuple(children)[source]
Parameters

children ([GLib.Variant]) – the items to make the tuple out of

Returns

a floating reference to a new GLib.Variant tuple

Return type

GLib.Variant

Creates a new tuple GLib.Variant out of the items in children. The type is determined from the types of children. No entry in the children array may be None.

If n_children is 0 then the unit tuple is constructed.

If the children are floating references (see GLib.Variant.ref_sink()), the new instance takes ownership of them as if via GLib.Variant.ref_sink().

New in version 2.24.

classmethod new_uint16(value)[source]
Parameters

value (int) – a #guint16 value

Returns

a floating reference to a new uint16 GLib.Variant instance

Return type

GLib.Variant

Creates a new uint16 GLib.Variant instance.

New in version 2.24.

classmethod new_uint32(value)[source]
Parameters

value (int) – a #guint32 value

Returns

a floating reference to a new uint32 GLib.Variant instance

Return type

GLib.Variant

Creates a new uint32 GLib.Variant instance.

New in version 2.24.

classmethod new_uint64(value)[source]
Parameters

value (int) – a #guint64 value

Returns

a floating reference to a new uint64 GLib.Variant instance

Return type

GLib.Variant

Creates a new uint64 GLib.Variant instance.

New in version 2.24.

classmethod new_variant(value)[source]
Parameters

value (GLib.Variant) – a GLib.Variant instance

Returns

a floating reference to a new variant GLib.Variant instance

Return type

GLib.Variant

Boxes value. The result is a GLib.Variant instance representing a variant containing the original value.

If child is a floating reference (see GLib.Variant.ref_sink()), the new instance takes ownership of child.

New in version 2.24.

classmethod parse(type, text, limit, endptr)[source]
Parameters
Raises

GLib.Error

Returns

a non-floating reference to a GLib.Variant, or None

Return type

GLib.Variant

Parses a GLib.Variant from a text representation.

A single GLib.Variant is parsed from the content of text.

The format is described here.

The memory at limit will never be accessed and the parser behaves as if the character at limit is the nul terminator. This has the effect of bounding text.

If endptr is non-None then text is permitted to contain data following the value that this function parses and endptr will be updated to point to the first character past the end of the text parsed by this function. If endptr is None and there is extra data then an error is returned.

If type is non-None then the value will be parsed to have that type. This may result in additional parse errors (in the case that the parsed value doesn’t fit the type) but may also result in fewer errors (in the case that the type would have been ambiguous, such as with empty arrays).

In the event that the parsing is successful, the resulting GLib.Variant is returned. It is never floating, and must be freed with GLib.Variant.unref().

In case of any error, None will be returned. If error is non-None then it will be set to reflect the error that occurred.

Officially, the language understood by the parser is “any string produced by GLib.Variant.print_()”.

There may be implementation specific restrictions on deeply nested values, which would result in a GLib.VariantParseError.RECURSION error. GLib.Variant is guaranteed to handle nesting up to at least 64 levels.

classmethod parse_error_print_context(error, source_str)[source]
Parameters
Returns

the printed message

Return type

str

Pretty-prints a message showing the context of a GLib.Variant parse error within the string for which parsing was attempted.

The resulting string is suitable for output to the console or other monospace media where newlines are treated in the usual way.

The message will typically look something like one of the following:

unterminated string constant:
(1, 2, 3, 'abc
          ^^^^

or

unable to find a common type:
[1, 2, 3, 'str']
 ^        ^^^^^

The format of the message may change in a future version.

error must have come from a failed attempt to GLib.Variant.parse() and source_str must be exactly the same string that caused the error. If source_str was not nul-terminated when you passed it to GLib.Variant.parse() then you must add nul termination before using this function.

New in version 2.40.

classmethod parse_error_quark()[source]
Return type

int

classmethod parser_get_error_quark()[source]
Return type

int

Same as g_variant_error_quark().

Deprecated since version ???: Use GLib.Variant.parse_error_quark() instead.

classmethod split_signature(signature)

Return a list of the element signatures of the topmost signature tuple.

If the signature is not a tuple, it returns one element with the entire signature. If the signature is an empty tuple, the result is [].

This is useful for e. g. iterating over method parameters which are passed as a single Variant.

byteswap()[source]
Returns

the byteswapped form of self

Return type

GLib.Variant

Performs a byteswapping operation on the contents of self. The result is that all multi-byte numeric data contained in self is byteswapped. That includes 16, 32, and 64bit signed and unsigned integers as well as file handles and double precision floating point values.

This function is an identity mapping on any value that does not contain multi-byte numeric data. That include strings, booleans, bytes and containers containing only these things (recursively).

While this function can safely handle untrusted, non-normal data, it is recommended to check whether the input is in normal form beforehand, using GLib.Variant.is_normal_form(), and to reject non-normal inputs if your application can be strict about what inputs it rejects.

The returned value is always in normal form and is marked as trusted. A full, not floating, reference is returned.

New in version 2.24.

check_format_string(format_string, copy_only)[source]
Parameters
  • format_string (str) – a valid GLib.Variant format string

  • copy_only (bool) – True to ensure the format string makes deep copies

Returns

True if format_string is safe to use

Return type

bool

Checks if calling g_variant_get() with format_string on self would be valid from a type-compatibility standpoint. format_string is assumed to be a valid format string (from a syntactic standpoint).

If copy_only is True then this function additionally checks that it would be safe to call GLib.Variant.unref() on self immediately after the call to g_variant_get() without invalidating the result. This is only possible if deep copies are made (ie: there are no pointers to the data inside of the soon-to-be-freed GLib.Variant instance). If this check fails then a g_critical() is printed and False is returned.

This function is meant to be used by functions that wish to provide varargs accessors to GLib.Variant values of uncertain values (eg: g_variant_lookup() or g_menu_model_get_item_attribute()).

New in version 2.34.

classify()[source]
Returns

the GLib.VariantClass of self

Return type

GLib.VariantClass

Classifies self according to its top-level type.

New in version 2.24.

compare(two)[source]
Parameters

two (GLib.Variant) – a GLib.Variant instance of the same type

Returns

negative value if a < b; zero if a = b; positive value if a > b.

Return type

int

Compares self and two.

The types of self and two are #gconstpointer only to allow use of this function with GLib.Tree, GLib.PtrArray, etc. They must each be a GLib.Variant.

Comparison is only defined for basic types (ie: booleans, numbers, strings). For booleans, False is less than True. Numbers are ordered in the usual way. Strings are in ASCII lexographical order.

It is a programmer error to attempt to compare container values or two values that have types that are not exactly equal. For example, you cannot compare a 32-bit signed integer with a 32-bit unsigned integer. Also note that this function is not particularly well-behaved when it comes to comparison of doubles; in particular, the handling of incomparable values (ie: NaN) is undefined.

If you only require an equality comparison, GLib.Variant.equal() is more general.

New in version 2.26.

dup_bytestring()[source]
Returns

a newly allocated string

Return type

bytes

Similar to GLib.Variant.get_bytestring() except that instead of returning a constant string, the string is duplicated.

The return value must be freed using GLib.free().

New in version 2.26.

dup_bytestring_array()[source]
Returns

an array of strings

Return type

[str]

Gets the contents of an array of array of bytes GLib.Variant. This call makes a deep copy; the return result should be released with GLib.strfreev().

If length is non-None then the number of elements in the result is stored there. In any case, the resulting array will be None-terminated.

For an empty array, length will be set to 0 and a pointer to a None pointer will be returned.

New in version 2.26.

dup_objv()[source]
Returns

an array of strings

Return type

[str]

Gets the contents of an array of object paths GLib.Variant. This call makes a deep copy; the return result should be released with GLib.strfreev().

If length is non-None then the number of elements in the result is stored there. In any case, the resulting array will be None-terminated.

For an empty array, length will be set to 0 and a pointer to a None pointer will be returned.

New in version 2.30.

dup_string()[source]
Returns

a newly allocated string, UTF-8 encoded

length

a pointer to a #gsize, to store the length

Return type

(str, length: int)

Similar to GLib.Variant.get_string() except that instead of returning a constant string, the string is duplicated.

The string will always be UTF-8 encoded.

The return value must be freed using GLib.free().

New in version 2.24.

dup_strv()[source]
Returns

an array of strings

Return type

[str]

Gets the contents of an array of strings GLib.Variant. This call makes a deep copy; the return result should be released with GLib.strfreev().

If length is non-None then the number of elements in the result is stored there. In any case, the resulting array will be None-terminated.

For an empty array, length will be set to 0 and a pointer to a None pointer will be returned.

New in version 2.24.

equal(two)[source]
Parameters

two (GLib.Variant) – a GLib.Variant instance

Returns

True if self and two are equal

Return type

bool

Checks if self and two have the same type and value.

The types of self and two are #gconstpointer only to allow use of this function with GLib.HashTable. They must each be a GLib.Variant.

New in version 2.24.

get_boolean()[source]
Returns

True or False

Return type

bool

Returns the boolean value of self.

It is an error to call this function with a self of any type other than %G_VARIANT_TYPE_BOOLEAN.

New in version 2.24.

get_byte()[source]
Returns

a #guint8

Return type

int

Returns the byte value of self.

It is an error to call this function with a self of any type other than %G_VARIANT_TYPE_BYTE.

New in version 2.24.

get_bytestring()[source]
Returns

the constant string

Return type

bytes

Returns the string value of a GLib.Variant instance with an array-of-bytes type. The string has no particular encoding.

If the array does not end with a nul terminator character, the empty string is returned. For this reason, you can always trust that a non-None nul-terminated string will be returned by this function.

If the array contains a nul terminator character somewhere other than the last byte then the returned string is the string, up to the first such nul character.

g_variant_get_fixed_array() should be used instead if the array contains arbitrary data that could not be nul-terminated or could contain nul bytes.

It is an error to call this function with a self that is not an array of bytes.

The return value remains valid as long as self exists.

New in version 2.26.

get_bytestring_array()[source]
Returns

an array of constant strings

Return type

[str]

Gets the contents of an array of array of bytes GLib.Variant. This call makes a shallow copy; the return result should be released with GLib.free(), but the individual strings must not be modified.

If length is non-None then the number of elements in the result is stored there. In any case, the resulting array will be None-terminated.

For an empty array, length will be set to 0 and a pointer to a None pointer will be returned.

New in version 2.26.

get_child_value(index_)[source]
Parameters

index (int) – the index of the child to fetch

Returns

the child at the specified index

Return type

GLib.Variant

Reads a child item out of a container GLib.Variant instance. This includes variants, maybes, arrays, tuples and dictionary entries. It is an error to call this function on any other type of GLib.Variant.

It is an error if index_ is greater than the number of child items in the container. See GLib.Variant.n_children().

The returned value is never floating. You should free it with GLib.Variant.unref() when you’re done with it.

Note that values borrowed from the returned child are not guaranteed to still be valid after the child is freed even if you still hold a reference to self, if self has not been serialized at the time this function is called. To avoid this, you can serialize self by calling GLib.Variant.get_data() and optionally ignoring the return value.

There may be implementation specific restrictions on deeply nested values, which would result in the unit tuple being returned as the child value, instead of further nested children. GLib.Variant is guaranteed to handle nesting up to at least 64 levels.

This function is O(1).

New in version 2.24.

get_data()[source]
Returns

the serialized form of self, or None

Return type

object or None

Returns a pointer to the serialized form of a GLib.Variant instance. The returned data may not be in fully-normalised form if read from an untrusted source. The returned data must not be freed; it remains valid for as long as self exists.

If self is a fixed-sized value that was deserialized from a corrupted serialized container then None may be returned. In this case, the proper thing to do is typically to use the appropriate number of nul bytes in place of self. If self is not fixed-sized then None is never returned.

In the case that self is already in serialized form, this function is O(1). If the value is not already in serialized form, serialization occurs implicitly and is approximately O(n) in the size of the result.

To deserialize the data returned by this function, in addition to the serialized data, you must know the type of the GLib.Variant, and (if the machine might be different) the endianness of the machine that stored it. As a result, file formats or network messages that incorporate serialized GLib.Variants must include this information either implicitly (for instance “the file always contains a %G_VARIANT_TYPE_VARIANT and it is always in little-endian order”) or explicitly (by storing the type and/or endianness in addition to the serialized data).

New in version 2.24.

get_data_as_bytes()[source]
Returns

A new GLib.Bytes representing the variant data

Return type

GLib.Bytes

Returns a pointer to the serialized form of a GLib.Variant instance. The semantics of this function are exactly the same as GLib.Variant.get_data(), except that the returned GLib.Bytes holds a reference to the variant data.

New in version 2.36.

get_double()[source]
Returns

a float

Return type

float

Returns the double precision floating point value of self.

It is an error to call this function with a self of any type other than %G_VARIANT_TYPE_DOUBLE.

New in version 2.24.

get_handle()[source]
Returns

a #gint32

Return type

int

Returns the 32-bit signed integer value of self.

It is an error to call this function with a self of any type other than %G_VARIANT_TYPE_HANDLE.

By convention, handles are indexes into an array of file descriptors that are sent alongside a D-Bus message. If you’re not interacting with D-Bus, you probably don’t need them.

New in version 2.24.

get_int16()[source]
Returns

a #gint16

Return type

int

Returns the 16-bit signed integer value of self.

It is an error to call this function with a self of any type other than %G_VARIANT_TYPE_INT16.

New in version 2.24.

get_int32()[source]
Returns

a #gint32

Return type

int

Returns the 32-bit signed integer value of self.

It is an error to call this function with a self of any type other than %G_VARIANT_TYPE_INT32.

New in version 2.24.

get_int64()[source]
Returns

a #gint64

Return type

int

Returns the 64-bit signed integer value of self.

It is an error to call this function with a self of any type other than %G_VARIANT_TYPE_INT64.

New in version 2.24.

get_maybe()[source]
Returns

the contents of self, or None

Return type

GLib.Variant or None

Given a maybe-typed GLib.Variant instance, extract its value. If the value is Nothing, then this function returns None.

New in version 2.24.

get_normal_form()[source]
Returns

a trusted GLib.Variant

Return type

GLib.Variant

Gets a GLib.Variant instance that has the same value as self and is trusted to be in normal form.

If self is already trusted to be in normal form then a new reference to self is returned.

If self is not already trusted, then it is scanned to check if it is in normal form. If it is found to be in normal form then it is marked as trusted and a new reference to it is returned.

If self is found not to be in normal form then a new trusted GLib.Variant is created with the same value as self. The non-normal parts of self will be replaced with default values which are guaranteed to be in normal form.

It makes sense to call this function if you’ve received GLib.Variant data from untrusted sources and you want to ensure your serialized output is definitely in normal form.

If self is already in normal form, a new reference will be returned (which will be floating if self is floating). If it is not in normal form, the newly created GLib.Variant will be returned with a single non-floating reference. Typically, GLib.Variant.take_ref() should be called on the return value from this function to guarantee ownership of a single non-floating reference to it.

New in version 2.24.

get_objv()[source]
Returns

an array of constant strings

Return type

[str]

Gets the contents of an array of object paths GLib.Variant. This call makes a shallow copy; the return result should be released with GLib.free(), but the individual strings must not be modified.

If length is non-None then the number of elements in the result is stored there. In any case, the resulting array will be None-terminated.

For an empty array, length will be set to 0 and a pointer to a None pointer will be returned.

New in version 2.30.

get_size()[source]
Returns

the serialized size of self

Return type

int

Determines the number of bytes that would be required to store self with GLib.Variant.store().

If self has a fixed-sized type then this function always returned that fixed size.

In the case that self is already in serialized form or the size has already been calculated (ie: this function has been called before) then this function is O(1). Otherwise, the size is calculated, an operation which is approximately O(n) in the number of values involved.

New in version 2.24.

get_string()[source]
Returns

the constant string, UTF-8 encoded

length

a pointer to a #gsize, to store the length

Return type

(str, length: int)

Returns the string value of a GLib.Variant instance with a string type. This includes the types %G_VARIANT_TYPE_STRING, %G_VARIANT_TYPE_OBJECT_PATH and %G_VARIANT_TYPE_SIGNATURE.

The string will always be UTF-8 encoded, will never be None, and will never contain nul bytes.

If length is non-None then the length of the string (in bytes) is returned there. For trusted values, this information is already known. Untrusted values will be validated and, if valid, a strlen() will be performed. If invalid, a default value will be returned — for %G_VARIANT_TYPE_OBJECT_PATH, this is "/", and for other types it is the empty string.

It is an error to call this function with a self of any type other than those three.

The return value remains valid as long as self exists.

New in version 2.24.

get_strv()[source]
Returns

an array of constant strings

Return type

[str]

Gets the contents of an array of strings GLib.Variant. This call makes a shallow copy; the return result should be released with GLib.free(), but the individual strings must not be modified.

If length is non-None then the number of elements in the result is stored there. In any case, the resulting array will be None-terminated.

For an empty array, length will be set to 0 and a pointer to a None pointer will be returned.

New in version 2.24.

get_type()[source]
Returns

a GLib.VariantType

Return type

GLib.VariantType

Determines the type of self.

The return value is valid for the lifetime of self and must not be freed.

New in version 2.24.

get_type_string()[source]
Returns

the type string for the type of self

Return type

str

Returns the type string of self. Unlike the result of calling g_variant_type_peek_string(), this string is nul-terminated. This string belongs to GLib.Variant and must not be freed.

New in version 2.24.

get_uint16()[source]
Returns

a #guint16

Return type

int

Returns the 16-bit unsigned integer value of self.

It is an error to call this function with a self of any type other than %G_VARIANT_TYPE_UINT16.

New in version 2.24.

get_uint32()[source]
Returns

a #guint32

Return type

int

Returns the 32-bit unsigned integer value of self.

It is an error to call this function with a self of any type other than %G_VARIANT_TYPE_UINT32.

New in version 2.24.

get_uint64()[source]
Returns

a #guint64

Return type

int

Returns the 64-bit unsigned integer value of self.

It is an error to call this function with a self of any type other than %G_VARIANT_TYPE_UINT64.

New in version 2.24.

get_variant()[source]
Returns

the item contained in the variant

Return type

GLib.Variant

Unboxes self. The result is the GLib.Variant instance that was contained in self.

New in version 2.24.

hash()[source]
Returns

a hash value corresponding to self

Return type

int

Generates a hash value for a GLib.Variant instance.

The output of this function is guaranteed to be the same for a given value only per-process. It may change between different processor architectures or even different versions of GLib. Do not use this function as a basis for building protocols or file formats.

The type of self is #gconstpointer only to allow use of this function with GLib.HashTable. self must be a GLib.Variant.

New in version 2.24.

is_container()[source]
Returns

True if self is a container

Return type

bool

Checks if self is a container.

New in version 2.24.

is_floating()[source]
Returns

whether self is floating

Return type

bool

Checks whether self has a floating reference count.

This function should only ever be used to assert that a given variant is or is not floating, or for debug purposes. To acquire a reference to a variant that might be floating, always use GLib.Variant.ref_sink() or GLib.Variant.take_ref().

See GLib.Variant.ref_sink() for more information about floating reference counts.

New in version 2.26.

is_normal_form()[source]
Returns

True if self is in normal form

Return type

bool

Checks if self is in normal form.

The main reason to do this is to detect if a given chunk of serialized data is in normal form: load the data into a GLib.Variant using GLib.Variant.new_from_data() and then use this function to check.

If self is found to be in normal form then it will be marked as being trusted. If the value was already marked as being trusted then this function will immediately return True.

There may be implementation specific restrictions on deeply nested values. GLib.Variant is guaranteed to handle nesting up to at least 64 levels.

New in version 2.24.

is_of_type(type)[source]
Parameters

type (GLib.VariantType) – a GLib.VariantType

Returns

True if the type of self matches type

Return type

bool

Checks if a value has a type matching the provided type.

New in version 2.24.

keys()
lookup_value(key, expected_type)[source]
Parameters
Returns

the value of the dictionary key, or None

Return type

GLib.Variant

Looks up a value in a dictionary GLib.Variant.

This function works with dictionaries of the type a{s*} (and equally well with type a{o*}, but we only further discuss the string case for sake of clarity).

In the event that self has the type a{sv}, the expected_type string specifies what type of value is expected to be inside of the variant. If the value inside the variant has a different type then None is returned. In the event that self has a value type other than v then expected_type must directly match the value type and it is used to unpack the value directly or an error occurs.

In either case, if key is not found in self, None is returned.

If the key is found and the value has the correct type, it is returned. If expected_type was specified then any non-None return value will have this type.

This function is currently implemented with a linear scan. If you plan to do many lookups then GLib.VariantDict may be more efficient.

New in version 2.28.

n_children()[source]
Returns

the number of children in the container

Return type

int

Determines the number of children in a container GLib.Variant instance. This includes variants, maybes, arrays, tuples and dictionary entries. It is an error to call this function on any other type of GLib.Variant.

For variants, the return value is always 1. For values with maybe types, it is always zero or one. For arrays, it is the length of the array. For tuples it is the number of tuple items (which depends only on the type). For dictionary entries, it is always 2

This function is O(1).

New in version 2.24.

print_(type_annotate)[source]
Parameters

type_annotate (bool) – True if type information should be included in the output

Returns

a newly-allocated string holding the result.

Return type

str

Pretty-prints self in the format understood by GLib.Variant.parse().

The format is described here.

If type_annotate is True, then type information is included in the output.

New in version 2.24.

ref()[source]
Returns

the same self

Return type

GLib.Variant

Increases the reference count of self.

New in version 2.24.

ref_sink()[source]
Returns

the same self

Return type

GLib.Variant

GLib.Variant uses a floating reference count system. All functions with names starting with g_variant_new_ return floating references.

Calling GLib.Variant.ref_sink() on a GLib.Variant with a floating reference will convert the floating reference into a full reference. Calling GLib.Variant.ref_sink() on a non-floating GLib.Variant results in an additional normal reference being added.

In other words, if the self is floating, then this call “assumes ownership” of the floating reference, converting it to a normal reference. If the self is not floating, then this call adds a new normal reference increasing the reference count by one.

All calls that result in a GLib.Variant instance being inserted into a container will call GLib.Variant.ref_sink() on the instance. This means that if the value was just created (and has only its floating reference) then the container will assume sole ownership of the value at that point and the caller will not need to unreference it. This makes certain common styles of programming much easier while still maintaining normal refcounting semantics in situations where values are not floating.

New in version 2.24.

store(data)[source]
Parameters

data (object) – the location to store the serialized data at

Stores the serialized form of self at data. data should be large enough. See GLib.Variant.get_size().

The stored data is in machine native byte order but may not be in fully-normalised form if read from an untrusted source. See GLib.Variant.get_normal_form() for a solution.

As with GLib.Variant.get_data(), to be able to deserialize the serialized variant successfully, its type and (if the destination machine might be different) its endianness must also be available.

This function is approximately O(n) in the size of data.

New in version 2.24.

take_ref()[source]
Returns

the same self

Return type

GLib.Variant

If self is floating, sink it. Otherwise, do nothing.

Typically you want to use GLib.Variant.ref_sink() in order to automatically do the correct thing with respect to floating or non-floating references, but there is one specific scenario where this function is helpful.

The situation where this function is helpful is when creating an API that allows the user to provide a callback function that returns a GLib.Variant. We certainly want to allow the user the flexibility to return a non-floating reference from this callback (for the case where the value that is being returned already exists).

At the same time, the style of the GLib.Variant API makes it likely that for newly-created GLib.Variant instances, the user can be saved some typing if they are allowed to return a GLib.Variant with a floating reference.

Using this function on the return value of the user’s callback allows the user to do whichever is more convenient for them. The caller will always receives exactly one full reference to the value: either the one that was returned in the first place, or a floating reference that has been converted to a full reference.

This function has an odd interaction when combined with GLib.Variant.ref_sink() running at the same time in another thread on the same GLib.Variant instance. If GLib.Variant.ref_sink() runs first then the result will be that the floating reference is converted to a hard reference. If GLib.Variant.take_ref() runs first then the result will be that the floating reference is converted to a hard reference and an additional reference on top of that one is added. It is best to avoid this situation.

unpack()

Decompose a GVariant into a native Python object.

unref()[source]

Decreases the reference count of self. When its reference count drops to 0, the memory used by the variant is freed.

New in version 2.24.