Python中定义只能实例化一个对象的类
2016-09-16
董付国
Python小屋
>>> class Single(object):
total = 0
def __init__(self):
if Single.total > 0:
raise Exception('You can create only one instance.')
Single.total += 1
>>> a = Single()
>>> b = Single()
Traceback (most recent call last):
File "<pyshell#40>", line 1, in <module>
b = Single()
File "<pyshell#38>", line 5, in __init__
raise Exception('You can create only one instance.')
Exception: You can create only one instance.
