Type hints in namedtuple
Just to be fair, NamedTuple
from typing
:
>>> from typing import NamedTuple
>>> class Point(NamedTuple):
... x: int
... y: int = 1 # Set default value
...
>>> Point(3)
Point(x=3, y=1)
equals to classic namedtuple
:
>>> from collections import namedtuple
>>> p = namedtuple('Point', 'x,y', defaults=(1, ))
>>> p.__annotations__ = {'x': int, 'y': int}
>>> p(3)
Point(x=3, y=1)
So, NamedTuple
is just syntax sugar for namedtuple
Below, you can find a creating NamedTuple
function from the source code of python 3.10
. As we can see, it uses collections.namedtuple
constructor and adds __annotations__
from extracted types:
def _make_nmtuple(name, types, module, defaults = ()):
fields = [n for n, t in types]
types = {n: _type_check(t, f"field {n} annotation must be a type")
for n, t in types}
nm_tpl = collections.namedtuple(name, fields,
defaults=defaults, module=module)
nm_tpl.__annotations__ = nm_tpl.__new__.__annotations__ = types
return nm_tpl
You can use typing.NamedTuple
From the docs
Typed version of
namedtuple
.
>>> import typing
>>> Point = typing.NamedTuple("Point", [('x', int), ('y', int)])
This is present only in Python 3.5 onwards
The prefered Syntax for a typed named tuple since 3.6 is
from typing import NamedTuple
class Point(NamedTuple):
x: int
y: int = 1 # Set default value
Point(3) # -> Point(x=3, y=1)
Edit
Starting Python 3.7, consider using dataclasses
(your IDE may not yet support them for static type checking):
from dataclasses import dataclass
@dataclass
class Point:
x: int
y: int = 1 # Set default value
Point(3) # -> Point(x=3, y=1)