re.search() vs re.match() - Python

When working with regular expressions (regex) in Python, re.search() and re.match() are two commonly used methods for pattern matching. Both are part of the re module but function differently. The key difference is that re.match() checks for a match only at the beginning of the string, while re.search() searches the entire string for the pattern. Example:

import re
s = '''We are learning regex with geeksforgeeks 
    regex is very useful for string matching.'''

a = re.match(r"regex", s)
print(a)

b = re.search(r"regex", s)
print(b)

None
<re.Match object; span=(16, 21), match='regex'>

Explanation:

• re.match() searches for "regex" only at the beginning of the string. Since it's not at the start, it returns None.
• re.search() searches for "regex" anywhere in the string. It finds it at index 16 and returns a match object.

When to use what?

Both re.match() and re.search() are powerful tools for pattern matching in strings. However, knowing when to use each can significantly improve both efficiency and accuracy in your code. Let’s dive into understanding when to use re.match() and re.search().

1. Use re.match(): When you're only interested in checking if a string begins with a specific pattern, you can use re.match(). This is especially useful for validating scenarios like file formats, prefixes or any fixed starting patterns in strings. For example, checking if a string starts with a particular number, letter, or keyword.

Example 1: Checking if a string starts with a number

import re
res = re.match(r"\d{4}", "2025 is the year")  # Matches "2025"
print(res)

<re.Match object; span=(0, 4), match='2025'>

Explanation: re.match(r"\d{4}", "2025 is the year") checks for four digits at the start of the string and since "2025" appears right at the beginning, it returns a match object.

Example 2: Matching a string that starts with a capital letter

import re
res= re.match(r"^[A-Z]", "Hello world")  # Matches
print(res)

<re.Match object; span=(0, 1), match='H'>

Explanation: re.match(r"^[A-Z]", "Hello world") checks if the string starts with an uppercase letter from A to Z and since "H" is uppercase at the beginning, it returns a match object.

2. Use re.search(): when the pattern can appear anywhere in the string. It's ideal for searching, filtering or scanning large texts like logs, documents or datasets.

Example 1: Searching for a keyword anywhere in the text

import re
res = re.search(r"error", "Server error at 5:00 PM")  # Matches "error"
print(res)

<re.Match object; span=(7, 12), match='error'>

Explanation: re.search(r"error", "Server error at 5:00 PM") looks for the substring "error" anywhere in the text and since it appears after "Server", it finds a match and returns a match object.

Example 2: Finding the first occurrence of 'apple' anywhere in the string.

import re
res = re.search(r"apple", "I have an apple and an orange.")
print(res) 

<re.Match object; span=(10, 15), match='apple'>

Explanation: re.search(r"apple", "I have an apple and an orange.") searches for the first occurrence of the substring "apple" in the string. Since "apple" appears in the text, it finds a match and returns a match object.

Difference between re.search() vs re.match()

In Python regex, re.match() and re.search() both find patterns, but differ in where they look. The table below highlights their key differences to help you choose the right one.