HashTable

class HashTable(*args, **kwargs)

The HashTable struct is an opaque data structure to represent a [Hash Table][glib-Hash-Tables]. It should only be accessed via the following functions.

Methods

class HashTable
add(hash_table: dict[None, None], key: None) → bool

This is a convenience function for using a HashTable as a set. It is equivalent to calling 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.

Added in version 2.32.

Parameters:

  • hash_table – a HashTable

  • key – a key to insert

contains(hash_table: dict[None, None], key: None) → bool

Checks if key is in hash_table.

Added in version 2.32.

Parameters:

  • hash_table – a HashTable

  • key – a key to check

destroy(hash_table: dict[None, None]) → None

Destroys all keys and values in the 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 HashTable with destroy notifiers using new_full(). In the latter case the destroy functions you supplied will be called on all keys and values during the destruction phase.

Parameters:

hash_table – a HashTable

find(hash_table: dict[None, None], predicate: Callable[[...], bool], *user_data: Any) → None

Calls the given function for key/value pairs in the 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. lookup(). So code that frequently issues find() or 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).

Added in version 2.4.

Parameters:

  • hash_table – a HashTable

  • predicate – function to test the key/value pairs for a certain property

  • user_data – user data to pass to the function

foreach(hash_table: dict[None, None], func: Callable[[...], None], *user_data: Any) → None

Calls the given function for each of the key/value pairs in the 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 foreach_remove().

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

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

Parameters:

  • hash_table – a HashTable

  • func – the function to call for each key/value pair

  • user_data – user data to pass to the function

foreach_remove(hash_table: dict[None, None], func: Callable[[...], bool], *user_data: Any) → int

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

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

Parameters:

  • hash_table – a HashTable

  • func – the function to call for each key/value pair

  • user_data – user data to pass to the function

insert(hash_table: dict[None, None], key: None, value: None) → bool

Inserts a new key and value into a HashTable.

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

Parameters:

  • hash_table – a HashTable

  • key – a key to insert

  • value – the value to associate with the key

lookup(hash_table: dict[None, None], key: None) → None

Looks up a key in a 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 lookup_extended().

Parameters:

  • hash_table – a HashTable

  • key – the key to look up

lookup_extended(hash_table: dict[None, None], lookup_key: None) → tuple[bool, None, None]

Looks up a key in the HashTable, returning the original key and the associated value and a gboolean 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 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.

Parameters:

  • hash_table – a HashTable

  • lookup_key – the key to look up

new_similar(other_hash_table: dict[None, None]) → dict[None, None]

Creates a new HashTable like 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.

Added in version 2.72.

Parameters:

other_hash_table – Another HashTable

remove(hash_table: dict[None, None], key: None) → bool

Removes a key and its associated value from a HashTable.

If the HashTable was created using 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.

Parameters:

  • hash_table – a HashTable

  • key – the key to remove

Returns:

0 if the file was successfully removed, -1 if an error occurred

remove_all(hash_table: dict[None, None]) → None

Removes all keys and their associated values from a HashTable.

If the HashTable was created using 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.

Added in version 2.12.

Parameters:

hash_table – a HashTable

replace(hash_table: dict[None, None], key: None, value: None) → bool

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

Parameters:

  • hash_table – a HashTable

  • key – a key to insert

  • value – the value to associate with the key

size(hash_table: dict[None, None]) → int

Returns the number of elements contained in the HashTable.

Parameters:

hash_table – a HashTable