Python字符串的运算及转义字符

字符串所用字符(’ ’ or " ")

>>> 'hello world'
'hello world'
>>> "hello world"
'hello world'
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为什么既有单引号又有双引号

打印出let’s go

>>> "let's go"
"let's go"
>>> 'let\'s go'
"let's go"
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终端打印多行

>>> '''
... hello world
... hello kaola
... hello python
... '''
'\nhello world\nhello kaola\nhello python\n'
>>> """
... hello world
... hello kaola
... hello python
... """
'\nhello world\nhello kaola\nhello python\n'
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字符串转义字符换行\n

>>> print(''' hello wolrd\n hello kaola\n hello python\n''')
 hello wolrd
 hello kaola
 hello python
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’ 单引号
\t 横向制表符(相当于tab)
\n 换行
\r 回车

打印出’hello \n world’

>>> print('hello \\n world')
hello \n world
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使用场景一：打印出磁盘目录 c:\northwide\northwest
除了加转义符号外，还可以在字符串前加r或者R

>>> print('c:\northwide\northwest')
c:
orthwide
orthwest
>>> print('c:\\northwide\\northwest')
c:\northwide\northwest
>>> print(r'c:\northwide\northwest')
c:\northwide\northwest
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合并字符串

1. ‘+’ (拼接)

>>> 'hello'+'world'
'helloworld'
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2. ‘*’(重复)

>>> 'hello'*3
'hellohellohello'
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3. ‘[n]’(取对应索引下字符)

>>> 'hello world'[3]
'l'
>>> 'hello world'[0]
'h'
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4. ‘[-n]’(从后往前数)

>>> 'hello world'[-5]
'w'
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5. ‘[m:n]’(截取一串字符)

>>> 'hello world'[0:4]
'hell'
>>> 'hello world'[0:-1]
'hello worl'
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6. ‘[m:]’(从索引m截取到字符串的末尾)

>>> 'hello world'[6:]
'world'
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7.‘[-m:]’ 如果字符串很长的情况下从末尾开始截取

>>> 'hello java python c# ruby'[-4:]
'ruby'
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