Index
🔍 What is RegEx?
Regular Expressions (RegEx) are patterns used to match text. Think of it as a smart search tool — you can search for things like:
- phone numbers
- emails
- specific words
- patterns in strings
🐍 Python and RegEx
Python has a built-in module called re for working with regular expressions.
import re
✅ Common Functions in re Module
| Function | Description |
|---|---|
re.search() | Search for a pattern in a string |
re.findall() | Find all matches in a string |
re.match() | Check if the pattern matches start |
re.sub() | Replace a pattern with something else |
📌 Example 1: Search for a word
import re
text = "Hello, my name is Sam."
result = re.search("Sam", text)
if result:
print("Match found!")
else:
print("No match.")
📌 Example 2: Find all digits
import re
text = "My phone number is 9876543210."
numbers = re.findall(r"\d", text)
print(numbers) # ['9', '8', '7', '6', '5', '4', '3', '2', '1', '0']
🧠 \d means any digit.
✨ Common RegEx Patterns
| Pattern | Meaning | Example Match |
|---|---|---|
\d | Any digit (0–9) | “5”, “9” |
\w | Any letter, digit, _ | “abc”, “123” |
\s | Any whitespace (space, tab) | ” “ |
. | Any character (except newline) | “a”, “3”, “!” |
^ | Start of string | ^Hello matches “Hello world” |
$ | End of string | world$ matches “Hello world” |
+ | One or more | \d+ matches “123” |
* | Zero or more | a* matches “”, “aaa” |
[] | Set of characters | [aeiou] matches any vowel |
📌 Example 3: Replace numbers with X
import re
text = "My score is 98"
new_text = re.sub(r"\d", "X", text)
print(new_text) # Output: My score is XX