Python Regex: re.search() VS re.findall() - GeeksforGeeks

11 Jan, 2022
Prerequisite: Regular Expression with Examples | Python
A Regular expression (sometimes called a Rational expression) is a sequence of characters that define a search pattern, mainly for use in pattern matching with strings, or string matching, i.e. “find and replace”-like operations. Regular expressions are a generalized way to match patterns with sequences of characters.
Module Regular Expressions (RE) specifies a set of strings (pattern) that matches it. To understand the RE analogy, MetaCharacters are useful, important and will be used in functions of module re.
There are a total of 14 metacharacters and will be discussed as they follow into functions:
\   Used to drop the special meaning of character
    following it (discussed below)
[]  Represent a character class
^   Matches the beginning
$   Matches the end
.   Matches any character except newline
?   Matches zero or one occurrence.
|   Means OR (Matches with any of the characters
    separated by it.
*   Any number of occurrences (including 0 occurrences)
+   One or more occurrences
{}  Indicate number of occurrences of a preceding RE 
    to match.
()  Enclose a group of REs

re.search() method either returns None (if the pattern doesn’t match), or a re.MatchObject that contains information about the matching part of the string. This method stops after the first match, so this is best suited for testing a regular expression more than extracting data.
Example:
Python3
# 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.")
Output:
Match at index 14, 21
Full match: June 24
Month: June
Day: 24

Return all non-overlapping matches of pattern in string, as a list of strings. The string is scanned left-to-right, and matches are returned in the order found.
Example:
Python3
# A Python program to demonstrate working of # findall() import re     # A sample text string where regular expression  # is searched. string = """Hello my Number is 123456789 and              my friend's number is 987654321"""    # A sample regular expression to find digits. regex = '\d+'                 match = re.findall(regex, string) print(match) 
Output:
['123456789', '987654321']

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