Python继承：将arg与kwarg混淆

Python inheritance: confusing arg with kwarg

如果我运行以下代码：

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class A(object) :

def __init__(self, x, y, z=3.0):
self.x = x
self.y = y
self.z = z

class B(A):

def __init__(self, a, b, c="c", *args, **kwargs):
super(B, self).__init__(*args, **kwargs)
self.a = a
self.b = b
self.c = c

if __name__=="__main__":

thing = B("a","b", 1, 2)

print thing.x # expect 1
print thing.y # expect 2
print thing.z # expect 3
print thing.a # expect a
print thing.b # expect b
print thing.c # expect c

相反，我得到：

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Traceback (most recent call last):
File"H:/Python/Random Scripts/python_inheritance.py", line 23, in <module>
thing = B(1,2,"a","b")
File"H:/Python/Random Scripts/python_inheritance.py", line 15, in __init__
super(B, self).__init__(*args, **kwargs)
TypeError: __init__() takes at least 3 arguments (2 given)

似乎python正在将第三个参数"a"解析为kwarg argment c而不是arg。我怎样才能得到我所期望的行为？

我当然可以：

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class B(A):

def __init__(self, a, b, *args, **kwargs):
self.c = kwargs.pop("c","c")
super(B, self).__init__(*args, **kwargs)
self.a = a
self.b = b

但从各个方面看都很可怕。