1.25 迷一样的字符串

示例一

# Python2.7
>>> a = "Hello_Python"
>>> id(a)
32045616
>>> id("Hello" + "_" + "Python")
32045616

# Python3.7
>>> a = "Hello_Python"
>>> id(a)
38764272
>>> id("Hello" + "_" + "Python")
32045616

示例二

>>> a = "MING"
>>> b = "MING"
>>> a is b
True

# Python2.7
>>> a, b = "MING!", "MING!"
>>> a is b
True

# Python3.7
>>> a, b = "MING!", "MING!"
>>> a is b
False

示例三

# Python2.7
>>> 'a' * 20 is 'aaaaaaaaaaaaaaaaaaaa'
True
>>> 'a' * 21 is 'aaaaaaaaaaaaaaaaaaaaa'
False

# Python3.7
>>> 'a' * 20 is 'aaaaaaaaaaaaaaaaaaaa'
True
>>> 'a' * 21 is 'aaaaaaaaaaaaaaaaaaaaa'
True