Python's common operation with strings

I. Slicing a string by index

A slice operation (slice) can get a substring (part of a string) from a string. We define a shard using a square bracket, a start offset start, a terminating offset end, and an optional step step.

Format: [Start:end:step]

• Start default value, if step is positive, the default is 0, if step is negative, then the default is-1
• End default value, if step is positive, the default is the end of the string position, if the step is positive, the default is the beginning of the string position
• Step default is 1. A positive number is sliced to the right, and if negative, slices to the left

Cases:

S = ' Abcdefghi '
print (s[::])
print (S[: 3:])
print (S[:3:-< span style= "color: #6897bb" >1])
print (S[ print (S[2::- 1])

Operation Result:

Abcdefghi
Abc
Ihgfe
Cdefghi
Cba

　　

Two. Common methods for string manipulation

All uppercase Str.upper () letters all lowercase str.lower () Case Flip str.swapcase () capitalize str.capitalize () Note: All letters are lowercase, and if the first character is a letter, the letter is converted to uppercase. Long characters are separated by a symbol (number, space), each separated by a string with the first letter capitalized Str.title () Note: All letters are lowercase, if the first character is a letter to the uppercase string to the center (return a original string centered, and use a space to fill the width of the new string. The default padding character is a space) Str.center (width[, Fillchar]) gets the string length L=len (s) determines whether the string starts with the specified substring str.startswith (str, Beg=0,end=len (String) Note: The range is [Beg,end] The index of the lookup element in the string Str.find (sub,_start,_end) Str.index (sub,_start,_end) Note: Find can not find return -1,index cannot find an error, The element is a substring, which returns the first letter index of the substring to delete the specified string beginning at the end of the specified character Str.strip (chars) str.rstrips (chars) str.lstrips (chars) Note: The default delete space Computes the number of occurrences of a character in a string Str.count (x,_start,_end) Split string Str.split (Sep,maxsplit)

Three. String format output

1. How to pass the% placeholder

Cases:

"My name is%s,
My age is%d,
My height is%d "% (' Zhang San ',176)
Print (MSG1)
"My name is% (name) s,
My age% (ages) d,
My height% (height) d ' '%{' name ':' Zhang San ', ' age': +,' height ':176}
Print (MSG2)

2. Use the Format method

Cases:

MSG3 ="' MSG3
My name is {},
My Age {},
My height {} ". Format (' Zhang San ',18,176)
Print (MSG3)
MSG4 ="' Msg4
My name is {0},
My age is {1},
 my height {2} ". Format ( ' Zhang San ' 18,176 "
 print (MSG4) 
 Msg5 = " "Msg5 
  my name is { Name}, 
  my Age {ages}, 
  my height {height} ". Format (name= ' Zhang San ' , age=18,height=176" 
 print (MSG5) 
 
 Span style= "font-size:15px" >  think: Can I write a formatted output method   
      

Python's common actions on strings