python dataclass asdict忽略没有类型注释的属性

Question

Python documentation explains how to use dataclass asdict but it does not tell that attributes without type annotations are ignored:

from dataclasses import dataclass, asdict

@dataclass
class C:
  a : int
  b : int = 3
  c : str = "yes"
  d = "nope"

c = C(5)
asdict(c)
# this returns
# {'a': 5, 'b': 3, 'c': 'yes'}
# note that d is ignored

How can I make d attribute appear in the returned dict without implementing the function myself?

Answer 1

You can use Any as type annotation. For example:

from typing import Any
from dataclasses import dataclass, asdict

@dataclass
class C:
  a : int
  b : int = 3
  c : str = "yes"
  d : Any = "nope"

c = C(5)
asdict(c)
# this returns
# {'a': 5, 'b': 3, 'c': 'yes', 'd': 'nope'}
# Now, d is included as well!

Answer 2

A cheesy and somewhat unprofessional way is to annotate it with any random string value.

So, for example:

from dataclasses import dataclass, asdict

@dataclass
class C:
  a : int
  b : int = 3
  c : str = "yes"
  d: 'help,, i dunno how [a]ny of this w@rks!!' = "nope"

c = C(5)
print(asdict(c))

# this returns
# {'a': 5, 'b': 3, 'c': 'yes', 'd': 'nope'}

With some thought, this can actually be simplified down to:

@dataclass
class C:
  a : int
  b : int = 3
  c : str = "yes"
  d: ... = "nope"