Python：断言变量是实例方法？

发布于 2024-08-01 17:10:18 字数 173 浏览 4 评论 0原文

如何检查变量是否是实例方法？我正在使用Python 2.5。

像这样的事情：

class Test:
    def method(self):
        pass

assert is_instance_method(Test().method)

原文

How can one check if a variable is an instance method or not? I'm using python 2.5.

Something like this:

class Test:
    def method(self):
        pass

assert is_instance_method(Test().method)

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破晓 2024-08-08 17:10:18

如果您想知道它是否正是实例方法，请使用以下函数。（它考虑在元类上定义并在类类方法上访问的方法，尽管它们也可以被视为实例方法）

import types
def is_instance_method(obj):
    """Checks if an object is a bound method on an instance."""
    if not isinstance(obj, types.MethodType):
        return False # Not a method
    if obj.im_self is None:
        return False # Method is not bound
    if issubclass(obj.im_class, type) or obj.im_class is types.ClassType:
        return False # Method is a classmethod
    return True

通常检查这是一个坏主意。能够与方法互换使用任何callable()更加灵活。

If you want to know if it is precisely an instance method use the following function. (It considers methods that are defined on a metaclass and accessed on a class class methods, although they could also be considered instance methods)

import types
def is_instance_method(obj):
    """Checks if an object is a bound method on an instance."""
    if not isinstance(obj, types.MethodType):
        return False # Not a method
    if obj.im_self is None:
        return False # Method is not bound
    if issubclass(obj.im_class, type) or obj.im_class is types.ClassType:
        return False # Method is a classmethod
    return True

Usually checking for that is a bad idea. It is more flexible to be able to use any callable() interchangeably with methods.

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习惯那些不曾习惯的习惯 2024-08-08 17:10:18

inspect.ismethod 是你想要的看看你是否确实有一个方法，而不仅仅是你可以调用的东西。

import inspect

def foo(): pass

class Test(object):
    def method(self): pass

print inspect.ismethod(foo) # False
print inspect.ismethod(Test) # False
print inspect.ismethod(Test.method) # True
print inspect.ismethod(Test().method) # True

print callable(foo) # True
print callable(Test) # True
print callable(Test.method) # True
print callable(Test().method) # True

如果参数是方法、函数（包括 lambda ）、具有 __call__ 的实例或类，则 callable 为 true。

方法具有与函数不同的属性（例如 im_class 和 im_self）。所以你要

assert inspect.ismethod(Test().method)

inspect.ismethod is what you want to find out if you definitely have a method, rather than just something you can call.

import inspect

def foo(): pass

class Test(object):
    def method(self): pass

print inspect.ismethod(foo) # False
print inspect.ismethod(Test) # False
print inspect.ismethod(Test.method) # True
print inspect.ismethod(Test().method) # True

print callable(foo) # True
print callable(Test) # True
print callable(Test.method) # True
print callable(Test().method) # True

callable is true if the argument if the argument is a method, a function (including lambdas), an instance with __call__ or a class.

Methods have different properties than functions (like im_class and im_self). So you want