> s1="hello"
> s2="hello"
> s1 is s2
True# 如果有空格，默认不启用intern机制
> s1="hell o"
> s2="hell o"
> s1 is s2
False# 如果一个字符串长度超过20个字符，不启动intern机制
> s1 = "a" * 20
> s2 = "a" * 20
> s1 is s2
True
> s1 = "a" * 21
> s2 = "a" * 21
> s1 is s2
False
> s1 = "ab" * 10
> s2 = "ab" * 10
> s1 is s2
True
> s1 = "ab" * 11
> s2 = "ab" * 11
> s1 is s2
False

s1 = "hell o"
s2 = "hell o"
print(s1 is s2) # True
s1 = "hell!*o"
s2 = "hell!*o"
print(s1 is s2) # True
s1 = "a" * 20
s2 = "a" * 20
print(s1 is s2) # True
s1 = "a" * 21
s2 = "a" * 21
print(s1 is s2) # False
s1 = "ab" * 10
s2 = "ab" * 10
print(s1 is s2) # True
s1 = "ab" * 11
s2 = "ab" * 11
print(s1 is s2) # False

> s1 = "hell"
> s2 = "hello"
> s1 + "o" is s2
False
> "hell" + "o" is s2
True
>
# 说明shell和IDE在这方面没有差异
s1 = "hell"
s2 = "hello"
print(s1 + "o" is s2) # False
print("hell" + "o" is s2) # True#因为"hell" + "o"在编译时已经变成了"hello"，而s1+"o"因为s1是一个变量，他们会在运行时进行拼接，所以没有被intern