Question

将self表达式添加到Python类的class Foo(object): def __init__(self, x): if x > 0: self.eval = lambda x: x else: self.eval = lambda x: x**2 return def compute(self, y): return self.eval(y)非常简单：

self.eval

就我而言，lambda稍微复杂一些，因此它不适合单行def。我需要self.eval。如何为def分配self.x = x函数？

出于性能原因，我希望不会存储if而不会将compute移到background-position。

Answer 1

您可以在任何地方定义功能：

class Foo(object):
    def __init__(self, x):
        if x > 0:
            def eval(y):
                return y
        else:
            def eval(y):
                return y**2
        self.eval = eval

    def compute(self, y):
        return self.eval(y)

Answer 2

generate a link。您可以将任何函数分配给变量：

Point

Answer 3

至少在Python 3中，向现有类添加方法是微不足道的。只需看看以下代码：

>>> class A:
    val = 2     # declare a class variable (will be the default value

>>> def func(self, x):       # declare a function that will be added as a method
    return self.val * x

>>> A.compute = func         # add the compute method to class A
>>> a = A()                  # create an instance
>>> a.val                    # control the value of the member
2
>>> a.compute(3)             # use the added method
6
>>> a.val=3                  # change the value of the variable for the specific instance
>>> a.compute(4)             # control that the new variable value is used
12

将非lamda函数添加到Python类的self中

3 个答案: