datacls 4.2.0

Slightly improved dataclasses

The Python built-in datacls is almost perfect, and this module just adds a little bit on top of it to smooth the rough edges a bit.

---

@datacls.mutable is @dataclasses.dataclass() , except:

• Dataclasses have three new instance method

  • asdict() like dataclasses.asdict()

  • astuple() like dataclasses.astuple()

  • replace() like dataclasses.replace()

• …and one new class method,

  • fields() like dataclasses.fields()

• xmod -ed for less cruft

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@datacls.immutable or just @datacls is like datacls.mutable except frozen=True by default.

---

datacls.field() just like dataclasses.field() except default_factory is now (also) a positional parameter.

Usage examples

import datacls
from typing import Dict

@datacls
class One:
    one: str = 'one'
    two: int = 2
    three: Dict = datacls.field(dict)  # Simplified `field`

#
# Three new instance methods
#
o = One()
assert o.asdict() == {'one': 'one', 'two': 2, 'three': {}}
assert o.astuple() == ('one', 2, {})

o2 = o.replace(one='seven', three={'nine': 9})
assert o2 == One('seven', 2, {'nine': 9})

#
# A new class method
#
assert [f.name for f in One.fields()] == ['one', 'two', 'three']

#
# Immutable by default
#
try:
    o.one = 'three'
except AttributeError:
    pass
else:
    raise AttributeError('Was mutable!')

@datacls.mutable
class OneMutable:
    one: str = 'one'
    two: int = 2
    three: Dict = datacls.field(dict)

om = OneMutable()
om.one = 'three'
assert str(om) == "OneMutable(one='three', two=2, three={})"

#
# These four new methods won't break your old dataclses:
#
@datacls
class Overloads:
    one: str = 'one'
    asdict: int = 1
    astuple: int = 1
    fields: int = 1
    replace: int = 1

o = Overloads()
assert ov.one == 'one'
assert ov.asdict == 1
assert ov.astuple == 1
assert ov.fields == 1
assert ov.replace == 1

# In this case, you can access them as functions on `datacls`:
assert (
    datacls.asdict(ov) ==
    {'asdict': 1, 'astuple': 1, 'fields': 1, 'one': 'one', 'replace': 1}
)

assert datacls.astuple(ov) == ('one', 1, 1, 1, 1)