Python Basics Tutorial String

• 1 basic string Operation
• 2 string formatting: Compact version
  • Font color= "#000000" >2.1 with string format operator
  • 2.2 format string template with string
• 3 string format: Full version
  • 3.1 conversion specifier
  • 3.2 simple conversion
  • 3.3 field width and precision
  • 3.4 symbol, align and 0 fill
• 4 string method
  • 4.1 find
  • 4.2 join
  • 4.3 lower
  • 4.4 Replace
  • 4.5 split
  • 4.6 strip
  • 4.7 translate

1 Basic string Operations

2. Description: String is also a sequence of one, so fragmentation, multiplication, index, length, maximum, minimum, judge membership can be applied to the string;
4. Note: The string is immutable, so it cannot be assigned a value;
5. Example

         
        
    
          
         
    
          
    
           
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   1:   >>> mystr="Test string"
   
   2:  ' t '
   
   3:  traceback (most Recent call Last:
   
   4:  "<pyshell#1>" in <module>
   
   5 :    ' t '
   
   6:  typeerror' str 'object   not support item assignment
   
   7:  >>>
    
          
    
         
         
        
   2String Formatting: Compact version

2.1 operator with string formatting

2. Description: String formatting using the string format operator percent ( % ) implementation, on the left-hand side of the operator is formatted string, the right is the value you want to be formatted;
4. Attention:
   1. Only tuples and dictionaries can be formatted into more than one value, and lists and other sequences are formatted as a value;
   2. A conversion specifier that marks where the conversion value needs to be inserted;
   3. If you want to output a percent semicolon in a formatted string, you need to use the %
5. Example:

          
         
    
           
          
    
           
    
            
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   1:#一般格式化
   
   2:>>> MyFormat ="Hello, my name is%s%s"
   
   3:>>> name = (' Bill ',' Gunn ')4:>>>Print(MyFormat% name)5:Hello, my Name isBill Gunn6:>>>7:
   
   8:#用列表格式化
   
   9:>>> MyFormat =' Hello, my name is%s '
   
   Ten:>>> name=[' Bill ',' Gunn ']One :>>>Print(MyFormat% name)A :Hello, my Name is[' Bill ',' Gunn ']:
   
   :#打印浮点数
   
   :>>>ImportMath:>>>Print("PI =%.5f"% pi):PI= 3.14159:
   
   :#打印百分号
   
   :>>>Print("%.2f%%"% 22.3):22.3%:>>>
    
    
           
    
          
          
         
   2.2Format strings with template of string

2. Description: Replaces a variable in a Unix shell with the substitute method, replacing the $foo in the string template with the passed in parameter foo
3. Example:

          
         
    
           
          
    
           
    
            
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   1:#从string模块中导入Template
   
   2:>>> fromStringImportTemplate3:#创建模板
   
   4:>>> MyFormat = Template ("My name is $name")5:#替换变量并打印
   
   6:>>>Print(Myformat.substitute (name="Bill Gunn."))7:My Name isBill Gunn8:>>>9:
   
   Ten:#输出美元符号的方法, enter two $ in the template
   
   One :>>> MyTemplate = Template ("The price is $$ $price")A :>>> Mytemplate.substitute (price=100):' The price is $ '
   
   :>>>:
   
   :#如果参数与后面的字符串相连, you need to enclose it in curly braces.
   
   :>>> fromStringImportTemplate:>>> MyTemplate = Template ("It ' s ${x}tastic!"):>>> Mytemplate.substitute (x=' Slum '):"It ' s slumtastic!"
   
   :>>>:
   
   To :#使用字典替换参数
   
   :>>> MyTemplate = Template ("My $property is $value"):>>> name = {}Num:>>> name["Property"] ="Name"
   
   :>>> name["Value"] ="Bill Gunn."
   
   :>>> Mytemplate.substitute (name):' My name is Bill Gunn '
   
   :>>>:
    
    
           
    
          
          
         
   3String formatting: Full version

2. Description: The right-hand operand of the string format operator if it is a tuple, then each element in the tuple must have a corresponding escape specifier in the format string.
3. Example:

         
        
    
          
         
    
          
    
           
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   1:>>> data =tuple(List("123"))2:>>> data3:(' 1 ',' 2 ',' 3 ')4:#格式化字符串中只有一个转义说明符, and there are three elements in the tuple, the conversion will complain
   
   5:&gt;&gt;&gt;Print(' data is%s '% data)6:Traceback (most recent call last):7:File"<pyshell#18>", Line 1, in&lt;module&gt;8:    Print(' data is%s '% data)9:TypeError: not  AllArguments converted during string formattingTen:#显示元组中的全部元素
   
   One :&gt;&gt;&gt;Print(' data is%s %s '%s '% data)A :Data is1 2 3:&gt;&gt;&gt;:
    
    
          
    
         
         
        
   3.1Conversion descriptor

1. Conversion descriptor

   Escape Descriptor	meaning
   D,i	Signed decimal integer
   O	Octal with no sign
   U	Decimal with no sign
   X	hexadecimal with no symbol (lowercase)
   X	hexadecimal with no symbol (uppercase)
   E	Floating-point number of scientific counting method (lowercase)
   E	Floating-point numbers of scientific notation (uppercase)
   F,f	Decimal floating-point numbers
   G	If the exponent is greater than-4 or less than the precision, the same as E, otherwise the same as F
   G	If the exponent is greater than-4 or less than the precision, the same as E, otherwise the same as F
   C	Given (accept integer or single character string)
   R	String (convert any Python object using repr)
   S	String (convert any Python object using str)

3.2 Simple conversion

1. Example:

          
         
    
           
          
    
           
    
            
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   1:   #十进制整数
   
   2:   Print ("The $%d" %)
   
   3:    is $
   
    4:  
   
    5:  #十六进制整数
   
   6:   Print ("Hex%x" %)
   
   7:   Hex C
   
    8:  
   
     
   
   9: #八进制整数 print   ("Oct%o" %)
   
   :  Oct
   
     >>>
   
    :  
    
           
    
          
          
         
   3.3Field width and precision

2. Description
   1. Field width: The minimum number of characters retained by the converted value;
   2. Field Precision: The number of decimal places that should be in the result after conversion;
   3. can use * as field width or precision
3. Example:

          
         
    
           
          
    
           
    
            
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   1:   #限制宽度
   
   2:   "%10f" % Math.PI
   
    3:  '  3.141593 '
   
    4:  
   
    5:   #限制小数位数
   
   6:   "%5.2f" % Math.PI
   
    7:  ' 3.14 '
   
    8:  
   
    9:   #用星号限制宽度和精度, in the following example, the width is 10 and the precision is 5
   
   . Ten:   '%*.*s ' ' Adfasdfadsfasdfasdfasdf ')
   
   One :   '     Adfas '
   
   A :   >>>
   
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   3.4symbols, alignment, and 0 padding

2. Description
   1. 0: The width is not enough with the number 0 fill;
   2. Minus sign: Left alignment;
   3. PLUS sign: Signs are marked either as positive or negative
   4. Space: Fill with space when the width is not enough;
3. Example:

          
         
    
           
          
    
           
    
            
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   1:#空白补0
   
   2:>>>Print("%010f"% Math.PI)3:003.1415934:
   
   5:#左对齐
   
   6:>>>"%-10.2f"% Math.PI7:' 3.14 '
   
   8:
   
   9:#空白右对齐
   
   Ten:>>>Print("% 5dn% 5d"% (123, 12))One :123A :12:
   
   :#显示正负符号
   
   :>>>Print("%+5dn%+5d"% (123,-123)):+123:-123:>>>:
    
    
           
    
          
          
         
   4String method

4.1 Find

2. Description: Used to find substrings in long strings and, if found, returns the first occurrence of the substring on the left and no return-1, when looking, you can also specify the range to look for in long strings, providing the starting index and end index as the parameter for the lookup;
4. Note: When looking, include the starting index position, but excluding the location of the end index;
5. Example:

          
         
    
           
          
    
           
    
            
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    1:  >>> String.ascii_letters  2:   ' abcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyz '   3:  >>> letters = string.ascii_letters  4:  &G T;>> letters.find ( ' AB ' )  5:   6:  >> ;> letters.find ( ' X ' , 30,-1)  7:   8:  >> ;> Letters.find ( "AB" , num)  9:  10:  
     
    
           
    
          
          
         
   4.2Join

2. Description: Concatenate the elements in the queue with strings, and the elements in the list must be strings;
3. Example:

    
           
          
    
            
           
    
            
    
             
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    1:  >> > data =  list  ( ' 123456 ' )  2:  >>> data  4:  >>>  "AB" . Join (data)  5:   ' 1ab2ab3ab4ab5ab6 '  6:  >>> 
    
            
    
           
    
           
          
     7: 

4.3 lower

2. Note: Converts the string to lowercase letters and returns, but the original string does not change;
4. Example:

    
           
         
    
            
          
    
           
    
            
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   < Span class= "Linenr" > 1:  >>> mystr=  "ABCD"   2:  >>> Mystr.lower ()  3:   ' ABCD '   4:  >>> mystr Span class= "Linenr" > 5:   ' ABCD '  6:  >>>  
    
    
           
    
          
    
           
         
     4.4  replace

1. Description: Returns the string after which all occurrences have been replaced
2. Example:

       
           
          
    
            
           
    
            
    
             
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   1:   "My name is Geng Qi"
   
   2:   >>> mystr.replace ("Geng Qi""Bill Gunn")
   
   3:  ' My name is Bill Gunn '
   
   4:  >>>
    
            
    
           
    
           
          
   4.5 Split

2. Description: Split the string into a sequence;
4. Note: If you do not provide a delimiter, whitespace is treated as a separator;
5. Example

          
         
    
           
          
    
           
    
            
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     #以加号为分割符   2:  >>> MyStr =  1+2+3+4+5+6   3:  >>> mystr.split ( ' + ' )  4:  [ ' 1 ' ,  ' 2 ' ,  ' 3 ' ,  ' 4 ' ,  ' 5 ' , span> ' 6 ' ]  5:   6:   #不提供分割符时, with whitespace as separator  
               
                 7:  >>> mystr = 
                 "This is a test string"  
                 8:  >>> mystr.split () 
                 9:  [
                 ' This ' , 
                 ' is ' , 
                 ' a ' , 
                 ' test ' , 
                 ' string '  ' 
                10:  >>> 
                11:  
               
    
    
           
    
          
          
         
   4.6Strip

2. Note: Remove both sides of the blank, you can also remove the specified characters;
3. Example:

          
         
    
           
          
    
           
    
            
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   1:   "           asdfad adfasf asdf                      "
   
    2:  >>> mystr
   
    3:  '     Tasdfad adfasf asdf       tt '
   
    4:  #去除空白符
   
   5:  >> > Mystr.strip ()
   
    6:  ' asdfad adfasf asdf '
   
    7:  
   
    8:   #去除指定字符
   
   9:   >>> Mystr.strip (' t ')
   
   :  '     tasdfad adfasf ' asdf       '
   
   One :    a
   
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   4.7Translate

2. Description: Translate is a word substitution, you can replace multiple characters at the same time
4. Example:

    
           
         
    
            
          
    
           
    
            
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   < Span class= "Linenr" > 1:  >>> table =  str . Maketrans ( ' CS ' ,  ' KZ '  ') Span class= "Linenr" > 2:  >>> table  3:  {115:122, 99:107}  4:  >>> " please don t knock at my door! .
   
   Translate (table)  5:   "Pleaze don ' t Knokk at my door!"  6: