regex_tut.py

# Meta Characters
# [] A set of characters
# \ Signals a special sequence (can also be used to escape special characters)
# . Any character (except newline character)
# ^ Starts with
# $ Ends with
# * Zero or more occurrences
# + One or more occurrences
# {} Exactly the specified number of occurrences
# | Either or
# () Capture and group
# Special Sequences
# \A Returns a match if the specified characters are at the beginning of the string
# \b Returns a match where the specified characters are at the beginning or at the end of a word r” ain\b.”
# \B Returns a match where the specified characters are present, but NOT at the beginning (or at the end) of a word
#
# \d Returns a match where the string contains digits (numbers from 0-9)
# \D Returns a match where the string DOES NOT contain digits
# \s Returns a match where the string contains a white space character
# \S Returns a match where the string DOES NOT contain a white space character
# \w Returns a match where the string contains any word characters (characters from a to Z, digits from 0-9,
# and the underscore _ character)
# \W Returns a match where the string DOES NOT contain any word characters
# \Z Returns a match if the specified characters are at the end of the string


import re

mystr = '''Tata Limited
Dr. David Landsman, executive director
18, Grosvenor Place
London SW1X 7HSc
Phone: +44 (20) 7235 8281
Fax: +44 (20) 7235 8727
Email: tata@tata.co.uk
Website: www.europe.tata.com
Directions: View map

Tata Sons, North America
1700 North Moore St, Suite 1520
Arlington, VA 22209-1911
USA
Phone: +1 (703) 243 9787
Fax: +1 (703) 243 9791
66-66
455-4545
Email: northamerica@tata.com 
Website: www.northamerica.tata.com
Directions: View map fass
harry bhai lekin
bahut hi badia aadmi haiaiin'''

# findall, search, split, sub, finditer
# patt = re.compile(r'fass')
# patt = re.compile(r'.adm')  # match any characters which follows adm
# patt = re.compile(r'^Tata')  # Checking if string start with characters specified
# patt = re.compile(r'iin$')  # Checking if string ends with characters specified
# patt = re.compile(r'ai*')  # Checking if string contains specified characters & Zero or more occurrences
# patt = re.compile(r'ai+')  # Checking if string contains specified characters & One or more occurrences
# patt = re.compile(r'ai{2}')  # Checking if string contains specified characters & Exactly the specified number of occurrences
# patt = re.compile(r'(ai){2}')  # Checking if string contains specified characters & Exactly the specified number of occurrences
patt = re.compile(r'(ai){2}|t')  # Checking if string contains specified characters & Exactly the specified number of occurrences & Either or |
matches = patt.finditer(mystr)
for match in matches:
    print(match)