python - 如何使非卡住数据类卡住，反之亦然？

我想知道使以下数据类 bar 卡住的任何简单方法。

@dataclass
class Bar:
    foo: int
bar = Bar(foo=1)

换句话说，我想要下面的函数 some_fn_to_freeze

frozen_bar = some_fn_to_freeze(bar)
frozen_bar.foo = 2 # Error

并且，反函数 some_fn_to_unfreeze

bar = som_fn_to_unfrozen(frozen_bar)
bar.foo = 3 # not Error

最佳答案

Python 数据类很棒，但 attrs 包是一个更灵活的替代方案，如果您能够使用第三方库。例如:

import attr

# Your class of interest.
@attr.s()
class Bar(object):
   val = attr.ib()

# A frozen variant of it.
@attr.s(frozen = True)
class FrozenBar(Bar):
   pass

# Three instances:
# - Bar.
# - FrozenBar based on that Bar.
# - Bar based on that FrozenBar.
b1 = Bar(123)
fb = FrozenBar(**attr.asdict(b1))
b2 = Bar(**attr.asdict(fb))

# We can modify the Bar instances.
b1.val = 777
b2.val = 888

# Check current vals.
for x in (b1, fb, b2):
    print(x)

# But we cannot modify the FrozenBar instance.
try:
    fb.val = 999
except attr.exceptions.FrozenInstanceError:
    print(fb, 'unchanged')

输出:

Bar(val=888)
FrozenBar(val=123)
Bar(val=999)
FrozenBar(val=123) unchanged

关于python - 如何使非卡住数据类卡住，反之亦然？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/56069359/