. - Any Character Except New Line
\d - Digit (0-9)
\D - Not a Digit (0-9)
\w - Word Character (a-z, A-Z, 0-9, _)
\W - Not a Word Character
\s - Whitespace (space, tab, newline)
\S - Not Whitespace (space, tab, newline)
\b - Word Boundary (blank in front of the word)
\B - Not a Word Boundary (starts in the middle of words)
^ - Beginning of a String
$ - End of a String
[] - Matches Characters in brackets
[^ ] - Matches Characters NOT in brackets
| - Either Or
( ) - Group
Quantifiers:
* - 0 or More
+ - 1 or More
? - 0 or One
{3} - Exact Number
{3,4} - Range of Numbers (Minimum, Maximum)
#### Sample Regexs ####
Email address-like pattern
[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\.[a-zA-Z0-9-.]+
Regular expression can be handled with re module
import re
pattern = re.compile(r'\d{3}-\d{3}-\d{4}') # finds an expression like 011-3210-5043
pattern.finditer(sentence_to_find_pattern) # returns an iterator of matched expressions (with position and expression)
pattern.findall(sentence_to_find_pattern) # returns a list of matched expression (if there is a group, then it returns a group list and if there are more than two groups, it returns a tupled group list)
pattern.sub(sub_expr, sentence_to_be_substituted) # substitues "sentence_to_be_substituted" with "sub_expr" (using pattern)import re
sentence_to_find_pattern='''
Phone Numbers
321-555-4321
123.555.1234
123*555*1234
800-555-1234
900-555-1234
End
'''
pattern = re.compile(r'\d{3}-\d{3}-\d{4}')
matches = pattern.finditer(sentence_to_find_pattern)
for match in matches:
print(match)Results
<re.Match object; span=(15, 27), match='321-555-4321'>
<re.Match object; span=(54, 66), match='800-555-1234'>
<re.Match object; span=(67, 79), match='900-555-1234'>
Reference: Corey Schafer