PYTHON

python regular expressions

import re

# returns a match object if found else None
txt = "Hello world"
x = re.search(r"[a-zA-z]+", txt)

if x:
    print("YES! We have a match!", x)
else:
    print("No match")
# output YES! We have a match! <re.Match object; span=(0, 5), match='Hello'>


# returns a list of all matches found - regular express finds all vowels in this example
txt = "This is a test"
x = re.findall(r"[aeiou]", txt)
print(x)
# output ['i', 'i', 'a', 'e']


# returns a list of all matches found - regular expression find is or test in string case-insensitive
txt = "This iS a Test"
x = re.findall("(is|test)", txt, flags=re.IGNORECASE)
print(x)
# output ['is', 'iS', 'Test']

txt = "This is a silly string"
# splits a string into a list using regular expression
x = re.split(r"silly", txt)
print(x)
# output ['This is a ', ' string']


# replace concatenated tototo with to
txt = "We need tototo run "
x = re.sub(r"(to)+", "to", txt)
print(x)
# output We need to run

re python3

import re
>>> m = re.search('(?<=abc)def', 'abcdef')
>>> m.group(0)
'def'

re python

>>> pattern = re.compile("o")
>>> pattern.match("dog")      # No match as "o" is not at the start of "dog".
>>> pattern.match("dog", 1)   # Match as "o" is the 2nd character of "dog".
<re.Match object; span=(1, 2), match='o'>

re module python

re module is used for regex operations. to import, type `import re`. Also, no need to install it since it's built-in in Python.

Python Regular Expressions

# A Python program to demonstrate working of re.match(). 
import re 
   
# Lets use a regular expression to match a date string 
# in the form of Month name followed by day number 
regex = r"([a-zA-Z]+) (d+)"
   
match = re.search(regex, "I was born on June 24") 
   
if match != None: 
   
    # We reach here when the expression "([a-zA-Z]+) (d+)" 
    # matches the date string. 
   
    # This will print [14, 21), since it matches at index 14 
    # and ends at 21. 
    print ("Match at index %s, %s" % (match.start(), match.end())) 
   
    # We us group() method to get all the matches and 
    # captured groups. The groups contain the matched values. 
    # In particular: 
    # match.group(0) always returns the fully matched string 
    # match.group(1) match.group(2), ... return the capture 
    # groups in order from left to right in the input string 
    # match.group() is equivalent to match.group(0) 
   
    # So this will print "June 24" 
    print ("Full match: %s" % (match.group(0))) 
   
    # So this will print "June" 
    print ("Month: %s" % (match.group(1))) 
   
    # So this will print "24" 
    print ("Day: %s" % (match.group(2)))
   
else: 
    print ("The regex pattern does not match.")

python re

if pattern := re.search("[iI] am (.*)", "I am tired"):
    print(f"Hi {pattern.group(1)}, I'm dad!")

python re

m = re.search(r'[cbm]at', 'aat')
print(m)

re python

>>> pattern = re.compile("o")
>>> pattern.match("dog")      # No match as "o" is not at the start of "dog".
>>> pattern.match("dog", 1)   # Match as "o" is the 2nd character of "dog".
<re.Match object; span=(1, 2), match='o'>