Python OOPs

Python SQLite

Examples

Others

Python OOPs

Python SQLite

Examples

Others



Python Regular Expression


Regular Expressions (regex or regexp) in Python are patterns used to match character combinations in strings. The re module provides a range of functions to work with regular expressions.

Import the re-module

import re
Pattern Description
. Matches any character except newline
^ Start of the string
$ End of the string
* Matches 0 or more repetitions
+ Matches 1 or more repetitions
? Matches 0 or 1 repetitions
{n} Matches exactly n repetitions
{n,} Matches n or more repetitions
{n,m} Matches between n and m times
[abc] Matches any character in the set
[^abc] Matches any character not in the set
\d Matches any digit (0-9)
\D Matches any non-digit
\w Matches any word character (a-z, A-Z, 0-9, _)
\W Matches any non-word character
\s Matches any whitespace
\S Matches any non-whitespace

1) re.match()

Matches a pattern at the start of the string. The group() method returns the complete matched subgroup by default or a tuple of matched subgroups depending on the number of arguments.

Example: 
result = re.match(r"hello", "hello world")
print(result.group())

Output

Hello

2) re.search()

Searches the entire string for a match and returns the first occurrence.

Example: 
result = re.search(r"world", "hello world")
print(result.group())

Output

World

3) re.findall()

Returns a list of all non-overlapping matches in the string.

Example: 
result = re.findall(r"o", "hello world")
print(result)

Output

['o', 'o']

4) re.finditer()

Returns an iterator yielding match objects for all matches.

Example: 
for match in re.finditer(r"o", "hello world"):
    print(match.start(), match.group())

Output

4 o
7 o

5) re.sub()

Replaces all occurrences of the pattern with a specified string.

Example: 
result = re.sub(r"world", "Python", "hello world")
print(result)

Output

hello Python

6) re.split()

Splits a string by the occurrences of the pattern.

Example: 
result = re.split(r"\s+", "hello world python")
print(result)

Output

['hello', 'world', 'python']

7) re.compile()

Compiles a regular expression pattern into a regex object for reuse.

Example: 
pattern = re.compile(r"\d+")
result = pattern.findall("123 abc 456")
print(result)

Output

['123', '456']