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Dict

Dict is a container compatible with the built-in dict, which serializes keys and values and stores them in a sqlite3 database. It preserves insertion order for all supported python versions.

Dict[KT, VT](...)

Constructor.

Type Parameters:

  • KT: key type
  • VT: value type

Arguments:

  • data: Mapping[KT, VT] or Iterable[Tuple[KT, VT]], optional, positional-only argument, defualt=None; Initial data. If None or no argument is given, persistent data is used as is if available, otherwise persistent data in the corresponding table is cleared and given data is stored instead.
  • connection: str or sqlite3.Connection, optional, default=None; If None, temporary file is automatically created. If connection is a str, it will be used as the sqlite3 database file name. You can pass a sqlite3.Connection directly.
  • table_name: str, optional, default=None; Table name of this container. If None, an auto-generated unique name will be used. Available characters are letters, numbers, and underscores (_).
  • key_serializer: Callable[[KT], bytes], optional, default=None; Function to serialize key. If None, pickle.dumps is used.
  • key_deserializer: Callable[[bytes], KT], optional, default=None; Function to deserialize key. If None, pickle.loads is used.
  • value_serializer: Callable[[VT], bytes], optional, default=None; Function to serialize value. If None, key_serializer is used.
  • value_deserializer: Callable[[bytes], VT], optional, default=None; Function to deserialize value. If None, key_deserializer is used.
  • persist: bool, optional, default=True; If True, table won't be deleted even when the object is deleted. If False, the table is deleted when this object is deleted.
  • pickling_strategy: PicklingStrategy, optional, default=PicklingStrategy.whole_table; Flag to control pickling method. See PicklingStrategy for more details.

len(d)

Return the number of items in d: Dict[KT, VT]

Return value:

int: The number of items in d

d[key]

Get item of d with key key. Raises a KeyError if key is not in the map.

Arguments:

  • key: KT; Key to retrieve corresponding value

Return value:

VT: Item of d with key key

d[key] = value

Set d[key] to value.

Arguments:

  • key: KT; Key to be set
  • value: VT; Value to be set

Return value:

None

del d[key]

Delete d[key].

Arguments:

  • key: KT; Key to be deleted

Return value:

None

key in d

Return whether if key is in d

Arguments:

  • key: KT; Key to be checked

Return value:

bool: True if key is in d and False otherwise.

key not in d

Return whether if key is not in d

Arguments:

  • key: KT; Key to be checked

Return value:

bool: True if key is not in d and False otherwise.

iter(d)

Return an iterator over the keys of d

Return value:

Iterator[KT]: an iterator over the keys of d

clear()

Remove all items from the dictionary

Return value:

None

copy()

Return a copy of the dictionary. The actual behavior is to create a table with a unique table name and copy the keys and the values to the new table. Therefore, unlike the built-in dict copy, the behavior is similar to deep copy. Be aware that the copied dictionary is volatile.

Return value:

Dict[KT, VT]: A volatile copy of the dictionary.

get(key[, default])

Return the value for key if key is in the dictionary, else default. If default is not given, it defaults to None, so that this method never raises a KeyError.

Arguments:

  • key: KT; Key to retrieve corresponding value if exists.
  • default: VT, optional, default=None; Default value in case that key is not in the dictionary

Return value:

VT: Item of the dictionary with key key if key is in the dictionary, default otherwise.

items()

Return a new view of the dictionary’s items (key-value pairs).

Return value:

ItemsView: View object of the dictionary's items

keys()

Return a new view of the dictionary's keys.

Return value:

KeysView[KT]: View object of the dictionary's keys.

pop(key[, default])

If key is in the dictionary, remove it and return its value, else return default. If default is not given and key is not in the dictionary, a KeyError is raised.

Arguments:

  • key: KT; Key to retrieve corresponding value if exists.
  • default: VT, optional, default=None; Default value in case that key is not in the dictionary

Return value:

VT: Item of the dictionary with key key if key is in the dictionary, default otherwise.

popitem()

Remove and return a key-value pair from the dictionary. Pairs are returned in LIFO order. If the dictionary is empty, raises a KeyError.

Return value:

Tuple[KT, VT]: Key-value pair that were last inserted into the dictionary

reversed(d)

Return a reverse iterator over the keys of the dictionary.

(provided only python version 3.8 and above)

Return value:

Iterator[KT]: Reverse iterator over the keys of the dictionary

setdefault(key[, default])

If key is in the dictionary, return its value. If not, insert key with a value of default and return default.

Arguments:

  • key: KT; Key to retrieve or set the value
  • default: VT, optional, default=None; Value to be set if key is not in the dictionary

Return value:

VT: Item of the dictionary with key key if key is in the dictionary, default otherwise.

update([other, **kwargs])

Update the dictionary with the key-value pairs from other, overwriting existing keys.

Arguments:

  • other: Mapping[KT, VT] or Iterable[Tuple[KT, VT]], optional; Key-value pairs to be added
  • kwargs: VT, optional; values to be added

Return value:

None

values()

Return a new view of the dictionary's values.

Return value:

ValuesView: View object of the dictionary's values

d | other

Create a new dictionary with the merged keys and values of d and other, which must both be dictionaries. The values of other take priority when d and other share keys. The return value is volatile by default.

(provided only python version 3.9 and above)

Arguments:

  • other: Mapping[KT, VT] or Iterable[Tuple[KT, VT]]; Key-value pairs to be merged

Return value:

Dict[KT, VT]: A new volatile dictionary object.

d |= other

Update the dictionary d with keys and values from other.

(provided only python version 3.9 and above)

Arguments:

  • other: Mapping[KT, VT] or Iterable[Tuple[KT, VT]]; Key-value pairs to be merged

Return value:

Dict[KT, VT]: The dictionary object.