python 类变量与实例变量，可变对象与不可变对象的实践

class E:
    s=''
    d=[]
    def __init__(self):
        self.dd=[]
aa=E()
aa.d.append('abc')
aa.dd.append('abc')
aa.s+='abc'
print(aa.d)
print(aa.dd)
print(aa.s)
print('='*20)
print(E.d)
print(E.s)
print('='*20)
aa=E()
aa.d.append('123')
aa.dd.append('123')
aa.s+='123'
print(aa.d)
print(aa.dd)
print(aa.s)

输出：

D:\Python37\python.exe D:/study____/PIC/test_import/a/a.py
['abc']
['abc']
abc
====================
['abc']

====================
['abc', '123']
['123']
123

Process finished with exit code 0

结论：

可变对象：list dict set

不可变对象：tuple string int float bool