python - __init__ 中的 UnboundLocalError

Question

我开始学习python，看不懂，错误在哪里

class Gun(object):
    def __init__(self, magazine=6):
        self.__dict__["magazine"] = magazine
        self.__dict__["ammo"] = ammo

错误日志

self.__dict__["ammo"] = ammo
UnboundLocalError: local variable 'ammo' referenced before assignment

Answer 1

错误出现在您的 __init__ 参数中。参数定义中没有ammo。

尝试以下操作:

class Gun(object):
    def __init__(self, magazine=6, ammo=5): # Now there is!
        self.__dict__["magazine"] = magazine
        self.__dict__["ammo"] = ammo

我建议不要修改对象__dict__。只需创建一个实例变量，它们做同样的事情，但代码更具可读性。

class Gun(object):
    def __init__(self, magazine=6, ammo=5):
        self.magazine = magazine
        self.ammo = ammo

In [3]: gun = Gun()

In [4]: gun.ammo
Out[4]: 5

In [5]: gun.magazine
Out[5]: 6

当然，您应该阅读 official tutorial on classes