yyj

a = "hello"

b = "HEllo"

c = "hello"

d = b.lower()

print(d)

print(id(a))

print(id(b))

print(id(c))

print(id(d))

print((a is c))

print((a is d))

hello

1292474520552

1292504355816

1292474520552

1292504355984

True

False

d将b全转化为小写，这时就会重新分配一个内存去保存d；而a和c的值一样，占用一个内存。