List of articles

• character string
• • Get a single character
  • Get multiple characters （ String truncation / String slice ）

character string

essentially , A string is made up of multiple characters , There is order between the characters , This sequence number is called the index （index）.Python Allows single or multiple characters in a string to be manipulated by index , For example, get the character at the specified index , Returns the index value of the specified character, etc .

Get a single character

After knowing the string name , Square brackets [ ] The corresponding characters can be accessed by using the index in , The specific syntax format is ：

strname[index]

strname Represents the string name ,index Indicates the index value .

Python Allows indexes to be used from both ends of a string ：

• When the left end of the string （ The beginning of the string ） When is the starting point , The index is from 0 Start counting ; The index of the first character of the string is 0, The index of the second character is 1, The index of the third string is 2 ……
• When at the right end of the string （ End of string ） When is the starting point , The index is from -1 Start counting ; The index of the penultimate character of the string is -1, The index of the penultimate character is -2, The index of the penultimate character is -3 ……

Take a look at the following example to demonstrate ：

url = 'http://c.biancheng.net/python/'
# Get the index as 10 The characters of 
print(url[10])
# Get the index as 6 The characters of 
print(url[-6])

Running results ：

i
y

Get multiple characters （ String truncation / String slice ）

Use [ ] In addition to getting a single character , You can also specify a range to get multiple characters , That is, a substring or fragment , The specific format is ：

strname[start : end : step]

A description of the parts ：

• strname： String to intercept ;
• start： Indicates the index of the first character to be intercepted （ Include this character when intercepting ）. If you don't specify , The default is 0, That is, intercept from the beginning of the string ;
• end： Indicates the index of the last character to be intercepted （ The character is not included in the interception ）. If you don't specify , The default is the length of the string ;
• step： Means from start Start with the character at the index , Every time step Get a character from a distance , until end The character derived from the search .step The default value is 1, When this value is omitted , The last colon can also be omitted .

【 example 1】 Basic usage ：

url = 'http://c.biancheng.net/java/'
# Get index from 7 Go to 22（ It doesn't contain 22） The string of 
print(url[7: 22]) # Output zy
# Get index from 7 Go to -6 The string of 
print(url[7: -6]) # Output zyit.org is very
# Get index from -21 To 6 The string of 
print(url[-21: -6])
# From the index 3 Start , every other 4 Characters take out a character , Until the index 22 until 
print(url[3: 22: 4])

Running results ：

c.biancheng.net
c.biancheng.net
c.biancheng.net
pcaen

【 example 2】 Advanced usage ,start、end、step All three parameters can be omitted ：

url = 'http://c.biancheng.net/java/'
# Get from index 5 Start , Substring up to the end 
print(url[7: ])
# Get from index -21 Start , Substring up to the end 
print(url[-21: ])
# Intercept the string from the beginning , Until the index 22 until 
print(url[: 22])
# every other 3 Characters take out a character 
print(url[:: 3])

Running results ：

c.biancheng.net/java/
c.biancheng.net/java/
http://c.biancheng.net
hp/bne.ta/