Dictionary class generic type settings

This page explains the Dictionary class key and value’s generic type settings.

Basic usage

You can specify the key and value’s type at the Dictionary type-annotation, as follows:

import apysc as ap

ap.Stage()
dict_value: ap.Dictionary[str, int] = ap.Dictionary({"a": 10})
a_value: int = dict_value["a"]

These generic type-annotations are sometimes helpful for checking with the mypy, Pylance, or other libraries and enhancing safety.

For example, the following code raises an error of value’s type when checking with the Pylance:

import apysc as ap

ap.Stage()
dict_value: ap.Dictionary[str, int] = ap.Dictionary({"a": 10})
a_value: str = dict_value["a"]

Expression of type "int" cannot be assigned to declared type "str"
  "int" is incompatible with "str"

Also, the following code raises an error of key’s type (str is required but int is specified):

import apysc as ap

ap.Stage()
dict_value: ap.Dictionary[str, int] = ap.Dictionary({"a": 10})
a_value: int = dict_value[10]

If you need to use multiple types and type checking, then use the Union, as follows:

Notes: Alternatively, use the | symbol, if you are using Python 3.10 or later) or Any type.

from typing import Union

import apysc as ap

ap.Stage()

# Accepting the str and int key types.
dict_value: ap.Dictionary[Union[int, str], int] = ap.Dictionary({"a": 10, 2: 20})
a_value: int = dict_value["a"]
b_value: int = dict_value[2]

from typing import Any

import apysc as ap

ap.Stage()

# Accepting all types by specifying the Any type.
dict_value: ap.Dictionary[Any, Any] = ap.Dictionary({"a": 10, 2: "b"})
a_value: int = dict_value["a"]
b_value: str = dict_value[2]