How to match a substring using a Python Regular Expression

Many Python Regular Expressions need to be matched with substrings, not only during replacement, but also in many places. Next we will learn in detail how to use a Python regular expression to obtain the desired matching substring.

Get the part of a string matched by the regex)

 
 

  
  
Regex = ur "..." # Regular Expression
  
  
Match = re. search (regex, subject)
  
  
If match:
  
  
Result = match. group ()
  
  
Else:
  
  
Result = ""
 
 

Get the part of a string matched by a capturing group)

 
 

  
  
Regex = ur "..." # Regular Expression
  
  
Match = re. search (regex, subject)
  
  
If match:
  
  
Result = match. group (1)
  
  
Else:
  
  
Result = ""
 
 

Get the part of a string matched by a named group)

 
 

  
  
Regex = ur "..." # Regular Expression
  
  
Match = re. search (regex, subject)
  
  
If match:
  
  
Result = match. group ("groupname ")
  
  
Else:
  
  
Result = ""
 
 

Put all matched substrings in the string into the array (Get an array of all regex matches in a string)

 
 

  
  
reresult = re.findall(regex, subject) 
 
 

Traverse all matched substrings (Iterate over all matches in a string)

 
 

  
  
for match in re.finditer(r"<(.*?)\s*.*?/\1>", subject)  
  
  
# match start: match.start()  
  
  
# match end (exclusive): match.end()  
  
  
# matched text: match.group() 
 
 

Create a regular expression object (Create an object to use the same regex for each operations)

 
 

  
  
rereobj = re.compile(regex) 
 
 

Python Regular Expression object version of use regex object for if/else branch whether (part of) a string can be matched)

 
 

  
  
rereobj = re.compile(regex)  
  
  
if reobj.search(subject):  
  
  
do_something()  
  
  
else:  
  
  
do_anotherthing() 
 
 

Python Regular Expression object version 2 use regex object for if/else branch whether a string can be matched entirely)

 
 

  
  
Rereobj = re. compile (r "\ Z") # End with \ Z at the end of the regular expression
  
  
If reobj. match (subject ):
  
  
Do_something ()
  
  
Else:
  
  
Do_anotherthing ()
 
 

The above is an introduction to the application of Python Regular Expressions in obtaining matched substrings.