GLib.HashTable

Fields

None

Methods

class

add (hash_table, key)

class

contains (hash_table, key)

class

destroy (hash_table)

class

find (hash_table, predicate, *user_data)

class

foreach (hash_table, func, *user_data)

class

foreach_remove (hash_table, func, *user_data)

class

foreach_steal (hash_table, func, *user_data)

class

insert (hash_table, key, value)

class

lookup (hash_table, key)

class

lookup_extended (hash_table, lookup_key)

class

new_similar (other_hash_table)

class

ref (hash_table)

class

remove (hash_table, key)

class

remove_all (hash_table)

class

replace (hash_table, key, value)

class

size (hash_table)

class

steal (hash_table, key)

class

steal_all (hash_table)

class

steal_extended (hash_table, lookup_key)

class

unref (hash_table)

Details

class GLib.HashTable

The GLib.HashTable struct is an opaque data structure to represent a Hash Table. It should only be accessed via the following functions.

classmethod add(hash_table, key)[source]
Parameters:
Returns:

True if the key did not exist yet

Return type:

bool

This is a convenience function for using a GLib.HashTable as a set. It is equivalent to calling GLib.HashTable.replace() with key as both the key and the value.

In particular, this means that if key already exists in the hash table, then the old copy of key in the hash table is freed and key replaces it in the table.

When a hash table only ever contains keys that have themselves as the corresponding value it is able to be stored more efficiently. See the discussion in the section description.

Starting from GLib 2.40, this function returns a boolean value to indicate whether the newly added value was already in the hash table or not.

New in version 2.32.

classmethod contains(hash_table, key)[source]
Parameters:
Returns:

True if key is in hash_table, False otherwise.

Return type:

bool

Checks if key is in hash_table.

New in version 2.32.

classmethod destroy(hash_table)[source]
Parameters:

hash_table ({object: object}) – a GLib.HashTable

Destroys all keys and values in the GLib.HashTable and decrements its reference count by 1. If keys and/or values are dynamically allocated, you should either free them first or create the GLib.HashTable with destroy notifiers using g_hash_table_new_full(). In the latter case the destroy functions you supplied will be called on all keys and values during the destruction phase.

classmethod find(hash_table, predicate, *user_data)[source]
Parameters:
Returns:

The value of the first key/value pair is returned, for which predicate evaluates to True. If no pair with the requested property is found, None is returned.

Return type:

object or None

Calls the given function for key/value pairs in the GLib.HashTable until predicate returns True. The function is passed the key and value of each pair, and the given user_data parameter. The hash table may not be modified while iterating over it (you can’t add/remove items).

Note, that hash tables are really only optimized for forward lookups, i.e. GLib.HashTable.lookup(). So code that frequently issues GLib.HashTable.find() or GLib.HashTable.foreach() (e.g. in the order of once per every entry in a hash table) should probably be reworked to use additional or different data structures for reverse lookups (keep in mind that an O(n) find/foreach operation issued for all n values in a hash table ends up needing O(n*n) operations).

New in version 2.4.

classmethod foreach(hash_table, func, *user_data)[source]
Parameters:

Calls the given function for each of the key/value pairs in the GLib.HashTable. The function is passed the key and value of each pair, and the given user_data parameter. The hash table may not be modified while iterating over it (you can’t add/remove items). To remove all items matching a predicate, use GLib.HashTable.foreach_remove().

The order in which GLib.HashTable.foreach() iterates over the keys/values in the hash table is not defined.

See GLib.HashTable.find() for performance caveats for linear order searches in contrast to GLib.HashTable.lookup().

classmethod foreach_remove(hash_table, func, *user_data)[source]
Parameters:
Returns:

the number of key/value pairs removed

Return type:

int

Calls the given function for each key/value pair in the GLib.HashTable. If the function returns True, then the key/value pair is removed from the GLib.HashTable. If you supplied key or value destroy functions when creating the GLib.HashTable, they are used to free the memory allocated for the removed keys and values.

See GLib.HashTableIter for an alternative way to loop over the key/value pairs in the hash table.

classmethod foreach_steal(hash_table, func, *user_data)[source]
Parameters:
Returns:

the number of key/value pairs removed.

Return type:

int

Calls the given function for each key/value pair in the GLib.HashTable. If the function returns True, then the key/value pair is removed from the GLib.HashTable, but no key or value destroy functions are called.

See GLib.HashTableIter for an alternative way to loop over the key/value pairs in the hash table.

classmethod insert(hash_table, key, value)[source]
Parameters:
Returns:

True if the key did not exist yet

Return type:

bool

Inserts a new key and value into a GLib.HashTable.

If the key already exists in the GLib.HashTable its current value is replaced with the new value. If you supplied a value_destroy_func when creating the GLib.HashTable, the old value is freed using that function. If you supplied a key_destroy_func when creating the GLib.HashTable, the passed key is freed using that function.

Starting from GLib 2.40, this function returns a boolean value to indicate whether the newly added value was already in the hash table or not.

classmethod lookup(hash_table, key)[source]
Parameters:
Returns:

the associated value, or None if the key is not found

Return type:

object or None

Looks up a key in a GLib.HashTable. Note that this function cannot distinguish between a key that is not present and one which is present and has the value None. If you need this distinction, use GLib.HashTable.lookup_extended().

classmethod lookup_extended(hash_table, lookup_key)[source]
Parameters:
Returns:

True if the key was found in the GLib.HashTable

orig_key:

return location for the original key

value:

return location for the value associated with the key

Return type:

(bool, orig_key: object, value: object)

Looks up a key in the GLib.HashTable, returning the original key and the associated value and a bool which is True if the key was found. This is useful if you need to free the memory allocated for the original key, for example before calling GLib.HashTable.remove().

You can actually pass None for lookup_key to test whether the None key exists, provided the hash and equal functions of hash_table are None-safe.

classmethod new_similar(other_hash_table)[source]
Parameters:

other_hash_table ({object: object}) – Another GLib.HashTable

Returns:

a new GLib.HashTable

Return type:

{object: object}

Creates a new GLib.HashTable like g_hash_table_new_full() with a reference count of 1.

It inherits the hash function, the key equal function, the key destroy function, as well as the value destroy function, from other_hash_table.

The returned hash table will be empty; it will not contain the keys or values from other_hash_table.

New in version 2.72.

classmethod ref(hash_table)[source]
Parameters:

hash_table ({object: object}) – a valid GLib.HashTable

Returns:

the passed in GLib.HashTable

Return type:

{object: object}

Atomically increments the reference count of hash_table by one. This function is MT-safe and may be called from any thread.

New in version 2.10.

classmethod remove(hash_table, key)[source]
Parameters:
Returns:

True if the key was found and removed from the GLib.HashTable

Return type:

bool

Removes a key and its associated value from a GLib.HashTable.

If the GLib.HashTable was created using g_hash_table_new_full(), the key and value are freed using the supplied destroy functions, otherwise you have to make sure that any dynamically allocated values are freed yourself.

classmethod remove_all(hash_table)[source]
Parameters:

hash_table ({object: object}) – a GLib.HashTable

Removes all keys and their associated values from a GLib.HashTable.

If the GLib.HashTable was created using g_hash_table_new_full(), the keys and values are freed using the supplied destroy functions, otherwise you have to make sure that any dynamically allocated values are freed yourself.

New in version 2.12.

classmethod replace(hash_table, key, value)[source]
Parameters:
Returns:

True if the key did not exist yet

Return type:

bool

Inserts a new key and value into a GLib.HashTable similar to GLib.HashTable.insert(). The difference is that if the key already exists in the GLib.HashTable, it gets replaced by the new key. If you supplied a value_destroy_func when creating the GLib.HashTable, the old value is freed using that function. If you supplied a key_destroy_func when creating the GLib.HashTable, the old key is freed using that function.

Starting from GLib 2.40, this function returns a boolean value to indicate whether the newly added value was already in the hash table or not.

classmethod size(hash_table)[source]
Parameters:

hash_table ({object: object}) – a GLib.HashTable

Returns:

the number of key/value pairs in the GLib.HashTable.

Return type:

int

Returns the number of elements contained in the GLib.HashTable.

classmethod steal(hash_table, key)[source]
Parameters:
Returns:

True if the key was found and removed from the GLib.HashTable

Return type:

bool

Removes a key and its associated value from a GLib.HashTable without calling the key and value destroy functions.

classmethod steal_all(hash_table)[source]
Parameters:

hash_table ({object: object}) – a GLib.HashTable

Removes all keys and their associated values from a GLib.HashTable without calling the key and value destroy functions.

New in version 2.12.

classmethod steal_extended(hash_table, lookup_key)[source]
Parameters:
Returns:

True if the key was found in the GLib.HashTable

stolen_key:

return location for the original key

stolen_value:

return location for the value associated with the key

Return type:

(bool, stolen_key: object, stolen_value: object)

Looks up a key in the GLib.HashTable, stealing the original key and the associated value and returning True if the key was found. If the key was not found, False is returned.

If found, the stolen key and value are removed from the hash table without calling the key and value destroy functions, and ownership is transferred to the caller of this method, as with GLib.HashTable.steal(). That is the case regardless whether stolen_key or stolen_value output parameters are requested.

You can pass None for lookup_key, provided the hash and equal functions of hash_table are None-safe.

The dictionary implementation optimizes for having all values identical to their keys, for example by using GLib.HashTable.add(). Before 2.82, when stealing both the key and the value from such a dictionary, the value was None. Since 2.82, the returned value and key will be the same.

New in version 2.58.

classmethod unref(hash_table)[source]
Parameters:

hash_table ({object: object}) – a valid GLib.HashTable

Atomically decrements the reference count of hash_table by one. If the reference count drops to 0, all keys and values will be destroyed, and all memory allocated by the hash table is released. This function is MT-safe and may be called from any thread.

New in version 2.10.