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leafcoderLife is short, use Python. V2EX 第 528113 号会员，加入于 2021-01-13 13:45:53 +08:00 |
leafcoder
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leafcoder 最近回复了
2021-03-01 10:10:38 +08:00 回复了 capbone 创建的主题 › Python › Python ：如何避免某个函数内的类反复进行实例化？ |
忽略第 3 条条件可以如下：
class C(object):
pass
class Demo(object):
def __new__(cls, *args, **kwargs):
inst = object.__new__(cls, *args, **kwargs)
if not hasattr(Demo, 'c_inst'):
c_inst = C(*args, **kwargs)
Demo.c_inst = c_inst
inst.c_inst = Demo.c_inst
return inst
def __init__(self, *args, **kwargs):
pass
for i in range(5):
o = Demo()
print(o, o.c_inst)
输出：
>>> (<__main__.Demo object at 0x7f7bd9e95310>, <__main__.C object at 0x7f7bd9e95350>)
>>> (<__main__.Demo object at 0x7f7bd9e95390>, <__main__.C object at 0x7f7bd9e95350>)
>>> (<__main__.Demo object at 0x7f7bd9e95310>, <__main__.C object at 0x7f7bd9e95350>)
>>> (<__main__.Demo object at 0x7f7bd9e95390>, <__main__.C object at 0x7f7bd9e95350>)
>>> (<__main__.Demo object at 0x7f7bd9e95310>, <__main__.C object at 0x7f7bd9e95350>)
class C(object):
pass
class Demo(object):
def __new__(cls, *args, **kwargs):
inst = object.__new__(cls, *args, **kwargs)
if not hasattr(Demo, 'c_inst'):
c_inst = C(*args, **kwargs)
Demo.c_inst = c_inst
inst.c_inst = Demo.c_inst
return inst
def __init__(self, *args, **kwargs):
pass
for i in range(5):
o = Demo()
print(o, o.c_inst)
输出：
>>> (<__main__.Demo object at 0x7f7bd9e95310>, <__main__.C object at 0x7f7bd9e95350>)
>>> (<__main__.Demo object at 0x7f7bd9e95390>, <__main__.C object at 0x7f7bd9e95350>)
>>> (<__main__.Demo object at 0x7f7bd9e95310>, <__main__.C object at 0x7f7bd9e95350>)
>>> (<__main__.Demo object at 0x7f7bd9e95390>, <__main__.C object at 0x7f7bd9e95350>)
>>> (<__main__.Demo object at 0x7f7bd9e95310>, <__main__.C object at 0x7f7bd9e95350>)
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