Regular Expressions Regex

Introduction

Python makes regular expressions available through the re module.

Regular expressions are combinations of characters that are interpreted as rules for matching substrings. For instance, the expression 'amount\D+\d+' will match any string composed by the word amount plus an integral number, separated by one or more non-digits, such as: amount=100, amount is 3, amount is equal to: 33, etc.

Syntax of Direct Regular Expressions

re.match(pattern, string, flag=0) # Out: match pattern at the beginning of string or None
re.search(pattern, string, flag=0) # Out: match pattern inside string or None
re.findall(pattern, string, flag=0) # Out: list of all matches of pattern in string or []
re.finditer(pattern, string, flag=0) # Out: same as re.findall, but returns iterator object
re.sub(pattern, replacement, string, flag=0) # Out: string with replacement (string or function) in place of pattern

Syntax of Precompiled Regular Expressions

precompiled_pattern = re.compile(pattern, flag=0)
precompiled_pattern.match(string) # Out: match at the beginning of string or None
precompiled_pattern.search(string) # Out: match anywhere in string or None
precompiled_pattern.findall(string) # Out: list of all matching substrings
precompiled_pattern.sub(string/pattern/function, string) # Out: replaced string

Found a mistake? Have a question or improvement idea? Let me know.

Table Of Contents