python中+=和=+的区别

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a+=1 代表在原值上更改

a=a+1相当于先定义一个变量，然后对新变量本身修改

#!/usr/bin/python
def test1(a):
        a+=a
        print(id(a))# display 140123195551624
        print(a)# display [11, 22, 11, 22]
def test2(a):
        a =a+a
        print(id(a))#display 140123195676424
        print(a)# display [11, 22, 11, 22, 11, 22, 11, 22]

nums = [11,22]
test1(nums)
print(nums)# display [11, 22, 11, 22]
test2(nums)
print(id(nums))#display 140123195551624
print(nums)# display [11, 22, 11, 22]