python只读属性怎么设置_Python只读属性

妖狐艹你老母 2023-01-01 06:51 220阅读 0赞

有一种方法可以避免这样的假设all users are consenting adults, and thus are responsible for using

things correctly themselves.

请参阅下面的我的更新

使用@property非常冗长，例如：class AClassWithManyAttributes:

'''refactored to properties'''

def \_\_init\_\_(a, b, c, d, e ...)

self.\_a = a

self.\_b = b

self.\_c = c

self.d = d

self.e = e

@property

def a(self):

return self.\_a

@property

def b(self):

return self.\_b

@property

def c(self):

return self.\_c

\# you get this ... it's long

使用No underscore: it's a public variable.

One underscore: it's a protected variable.

Two underscores: it's a private variable.

除了最后一个，这是一个惯例。如果你真的努力了，你仍然可以用双下划线访问变量。

那我们该怎么办？我们是否放弃在Python中使用只读属性？

瞧！read\_only\_properties装饰工来救人！@read\_only\_properties('readonly', 'forbidden')

class MyClass(object):

def \_\_init\_\_(self, a, b, c):

self.readonly = a

self.forbidden = b

self.ok = c

m = MyClass(1, 2, 3)

m.ok = 4

\# we can re-assign a value to m.ok

\# read only access to m.readonly is OK

print(m.ok, m.readonly)

print("This worked...")

\# this will explode, and raise AttributeError

m.forbidden = 4

你问：Where is read\_only\_properties coming from?def read\_only\_properties(\*attrs):

def class\_rebuilder(cls):

"The class decorator"

class NewClass(cls):

"This is the overwritten class"

def \_\_setattr\_\_(self, name, value):

if name not in attrs:

pass

elif name not in self.\_\_dict\_\_:

pass

else:

raise AttributeError("Can't modify \{\}".format(name))

super().\_\_setattr\_\_(name, value)

return NewClass

return class\_rebuilder

更新

我从来没想到这个答案会受到如此多的关注。令人惊讶的是。这鼓励我创建一个可以使用的包。$ pip install read-only-properties

在python shell中：In \[1\]: from rop import read\_only\_properties

In \[2\]: @read\_only\_properties('a')

...: class Foo:

...: def \_\_init\_\_(self, a, b):

...: self.a = a

...: self.b = b

...:

In \[3\]: f=Foo('explodes', 'ok-to-overwrite')

In \[4\]: f.b = 5

In \[5\]: f.a = 'boom'

\---------------------------------------------------------------------------

AttributeError Traceback (most recent call last)

in ()

\----> 1 f.a = 'boom'

/home/oznt/.virtualenvs/tracker/lib/python3.5/site-packages/rop.py in \_\_setattr\_\_(self, name, value)

116 pass

117 else:

\--> 118 raise AttributeError("Can't touch \{\}".format(name))

119

120 super().\_\_setattr\_\_(name, value)

AttributeError: Can't touch a

python只读属性怎么设置_Python只读属性

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