Type hints in Python (4)

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*Memo:

• My post explains type hints (1).
• My post explains type hints (2).
• My post explains type hints (3).
• My post explains type hints (5).
• My post explains type hints (6).

list, tuple, set, frozenset, dict, str, bytes, bytearray, range, Container, Hashable, Iterable, Iterator, Reversible, Generator, Sized, Collection, Sequence, MutableSequence, Set, MutableSet, Mapping, MutableMapping, MappingView, ItemsView, KeysView and ValuesView can be used for iterables as shown below:

*Memo:

• For str, bytes, bytearray, range, Hashable, Sized and MappingView:
  • Each has no arguments.
  • Hashable cannot be used for an iterator even it's immutable according to the issue.
  • MappingView accepts itself, dict_keys(KeysView), dict_values(ValuesView) and dict_items(ItemsView).
• For list, set, frozenset, Container, Iterable, Iterator, Reversible, Generator, Collection, Sequence, MutableSequence, Set, MutableSet, KeysView and ValuesView:
  • The 1st argument is type(Required:-Type:Type):
    • It's a type.
    • Don't use type=.
  • Use Iterator instead of iter because type checkers don't support iter.
  • Use KeysView and ValuesView instead of dict_keys and dict_values respectively because type checkers don't support dict_keys and dict_values in _collections_abc.
• For dict, Mapping, MutableMapping and ItemsView:
  • The 1st argument is keytype(Required:-Type:list(Type)):
    • It's a key type.
    • Don't use keytype=.
  • The 2nd argument is valuetype(Required-Type:Type)):
    • It's a value type.
    • Don't use valuetype=.
  • Use ItemsView instead of dict_items because type checkers don't support dict_items in _collections_abc.
• For tuple:
  • The 1st arguments are *types(Required:-Type:Type):
    • It's one or more types.
    • Only in the 2nd argument, ... (but not Ellipsis) can be used to accept the zero or more arguments of a type.
    • Don't use any keywords like *types=, types=, etc.
  • tuple is special so each type must be specified for each value.
  • An unpacked tuple is possible.
  • The doc explains the type hint with a tuple.

<list>:

from collections.abc import (
    MutableSequence, Sequence, Reversible,
    Collection, Sized, Container, Iterable
)

v: list[int] = [0, 1, 2, 3, 4]
# v: MutableSequence[int] = [0, 1, 2, 3, 4]
# v: Sequence[int] = [0, 1, 2, 3, 4]
# v: Reversible[int] = [0, 1, 2, 3, 4]
# v: Collection[int] = [0, 1, 2, 3, 4]
# v: Sized = [0, 1, 2, 3, 4]
# v: Container[int] = [0, 1, 2, 3, 4]
# v: Iterable[int] = [0, 1, 2, 3, 4]

print(v) 
# No error

print(v[0], v[1:3])
# Reversible, Collection, Sized, Container and Iterable get error.

print(*v)
# Sized and Container get error.

print(v+v)
# MutableSequence, Sequence, Reversible, Collection,
# Sized, Container, Iterable get error

<tuple>:

from collections.abc import (
    Hashable, Sequence, Reversible, Collection, Sized, Container, Iterable
)

v: tuple[int, ...] = (0, 1, 2, 3, 4)
# v: tuple[int, int, int, int, int] = (0, 1, 2, 3, 4)
# v: tuple[int, int, *tuple[int, ...]] = (0, 1, 2, 3, 4)
# v: tuple[int, int, *tuple[int, int, int]] = (0, 1, 2, 3, 4)
# v: Hashable = (0, 1, 2, 3, 4)
# v: Sequence[int] = (0, 1, 2, 3, 4)
# v: Reversible[int] = (0, 1, 2, 3, 4)
# v: Collection[int] = (0, 1, 2, 3, 4)
# v: Sized = (0, 1, 2, 3, 4)
# v: Container[int] = (0, 1, 2, 3, 4)
# v: Iterable[int] = (0, 1, 2, 3, 4)

print(v) 
# No error

print(v[0], v[1:3])
# Hashable, Reversible, Collection, Sized, Container and Iterable get error.

print(*v)
# Hashable, Sized and Container get error.

print(v+v)
# Hashable, Sequence, Reversible, Collection,
# Sized, Container and Iterable get error.

<set>:

from collections.abc import (
    MutableSet, Set, Collection, Sized, Container, Iterable
)

v: set[int] = {0, 1, 2, 3, 4}
# v: MutableSet[int] = {0, 1, 2, 3, 4}
# v: Set[int] = {0, 1, 2, 3, 4}
# v: Collection[int] = {0, 1, 2, 3, 4}
# v: Sized = {0, 1, 2, 3, 4}
# v: Container[int] = {0, 1, 2, 3, 4}
# v: Iterable[int] = {0, 1, 2, 3, 4}

print(v)
# No error

print(*v)
# Sized and Container get error.

print(v | v)
# Collection, Sized, Container and Iterable get error.

<frozenset>:

from collections.abc import (
    Set, Hashable, Collection, Sized, Container, Iterable
)

v: frozenset[int] = frozenset([0, 1, 2, 3, 4])
# v: Set[int] = frozenset([0, 1, 2, 3, 4])
# v: Hashable = frozenset([0, 1, 2, 3, 4])
# v: Collection[int] = frozenset([0, 1, 2, 3, 4])
# v: Sized = frozenset([0, 1, 2, 3, 4])
# v: Container[int] = frozenset([0, 1, 2, 3, 4])
# v: Iterable[int] = frozenset([0, 1, 2, 3, 4])

print(v)
# No error

print(*v)
# Hashable, Sized and Container get error.

print(v | v)
# Hashable, Collection, Sized, Container and Iterable get error.