is是判断地址相同，==是判断值相同
a=1
b=a
print(b is a)#True
print(a is b)#True
print(b == a)#True
print('\n')
c=1
d=1
print(d is c)#True#why?
print(c is d)#True
print(c == d)#True
print('\n')
e=1
f=2
print(e is f)#False
print(f is e)#False
print(e == f)#False
print('\n')
g=[1]
h=[1]
print(h is g)#False
print(g is h)#False
print(g == h)#True
print('\n')
i=[1]
j=i
print(i is j)#True
print(j is i)#True
print(i == j)#True
print('\n')
'''answer for why: Python会对比较小的对象缓存，下次用到比较小的对象时，会去缓存区查找，如果找到，不会再开辟新的内存，而是继续把小对象的地址赋给新的值'''
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