Python Regular Expressions
Regular expressions (regex) are a powerful tool for matching patterns in text. Python provides support for regular expressions through the built-in re module.
The re Module
To use regular expressions in Python, you need to import the re module.
import reCommon Functions
re.search()
Searches the string for a match and returns a Match object if there is a match.
txt = "The rain in Spain"
x = re.search("^The.*Spain$", txt)
if x:
print("YES! We have a match!")
else:
print("No match")re.findall()
Returns a list containing all matches.
txt = "The rain in Spain"
x = re.findall("ai", txt)
print(x) # Output: ['ai', 'ai']re.split()
Returns a list where the string has been split at each match.
txt = "The rain in Spain"
x = re.split("\s", txt)
print(x) # Output: ['The', 'rain', 'in', 'Spain']re.sub()
Replaces one or many matches with a string.
txt = "The rain in Spain"
x = re.sub("\s", "9", txt)
print(x) # Output: The9rain9in9SpainMetacharacters
[]: A set of characters (e.g.,[a-m])\: Signals a special sequence (e.g.,\d).: Any character (except newline character)^: Starts with$: Ends with*: Zero or more occurrences+: One or more occurrences?: Zero or one occurrences{}: Exactly the specified number of occurrences|: Either or(): Capture and group
Special Sequences
\d: Returns a match where the string contains digits (numbers from 0-9).\w: Returns a match where the string contains any word characters (characters from a to Z, digits from 0-9, and the underscore _ character).\s: Returns a match where the string contains a white space character.