'''
    regex.py

    Jeff Ondich, 16 Jan 2009
    Tianna Avery, November 2018, updated for Python 3

    This program gives a brief illustration of a few of the
    features of the re (regular expression) module.

    The re module has a lot of complicated and powerful features.
    You can find the official documentation here:

    https://docs.python.org/3/library/re.html
'''

import re

# We're going to look for stuff inside the following string.
s = 'a frog, a dog, and a hog, were agog on the log in the bog'

print('This program will perform regular expression searches on the string:')
print(f'  "{s}"')
print()

# Find a simple match
regex = 'hog'
print(f'Looking for "{regex}".')
result = re.search(regex, s)
if result:
    print(f'The first match goes from index {result.start()} to {result.end()-1}')
else:
    print('No match found.')
print()

# Find a sequence of letters ending in "og".
regex = '(\w*og)\W'
print(f'Looking for "{regex}".')
result = re.search(regex, s)
if result:
    print(f'Found "{result.groups()[0]}"')
else:
    print('No match found.')
print()

# Find all the sequences of letters ending in "og".
regex = '\w*og\\b' # Any guesses why we do \\b instead of \b?
print(f'Looking for all occurrences of "{regex}".')
result = re.findall(regex, s)
if result:
    print(result)
else:
    print('No match found.')
print()

# Split the string on a pattern.
regex = '\w*og\\b'
print(f'Splitting the string on all occurrences of "{regex}".')
result = re.split(regex, s)
if result:
    print(result)
else:
    print('No match found.')
print

# Replace all og-words with OGWORD.
regex = '\w*og\\b'
print(f'Splitting the string on all occurrences of "{regex}".')
print(re.sub(regex, 'OGWORD', s))
print()