Python中字符串二三事

Posted 2021-02-17 月为暮

首先说两个运算符：

" == " 运算符测试值的等价性，递归地比较所有内嵌对象

" is " 表达式测试对象的同一性，测试两者是否为同一对象（是否为同一地址）

Python内部会对临时存储并重复使用的段字符串做优化，在PyCharm中优化的很好

下边是在PyCharm中运行的

s1 = ‘hello‘
s2 = ‘hello‘
print(s1 is s2)

s1 = ‘hello world‘
s2 = ‘hello world‘
print(s1 is s2)

s1 = ‘h e l l o‘
s2 = ‘h e l l o‘
print(s1 is s2)

s1 = ‘a longer string‘
s2 = ‘a longer string‘
print(s1 is s2)

s1 = ‘hello world good morning‘
s2 = ‘hello world good morning‘
print(s1 is s2)

　　

True
True
True
True
True

　　

下边是在Python交互器中运行的现象。

>>> s1 = "spam"
>>> s2 = "spam"
>>> s1 is s2
True
>>> s1 = "sp am"
>>> s2 = "sp am"
>>> s1 is s2
False
>>> s1 = ‘ ‘
>>> s2 = ‘ ‘
>>> s1 is s2
True
>>> s1 = ‘  ‘
>>> s2 = ‘  ‘
>>> s1 is s2
False
>>> s1 = ‘kkkkkkkkkkkkkkkkkkkkk‘
>>> s2 = ‘kkkkkkkkkkkkkkkkkkkkk‘
>>> s1 is s2
True
>>> s1 = ‘		‘
>>> s2 = ‘		‘
>>> s1 is s2
False
>>> s1 = ‘
‘
>>> s2 = ‘
‘
>>> s1 is s2
True

 

没试验太多数据，老哥们要是有新的发现也可以跟我说