Python RegEx

Use the built-in re module in all tasks.

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1) Import and Match

Write a program to import re and check if the string "hello" matches the pattern "hello" using re.match().

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2) Search for Substring

Ask the user for a text. Search for the substring "cat" using re.search() and print whether it was found.

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3) Find All Digits

Given the string "a1b2c3", use re.findall() to extract all digits.

Expected:

['1', '2', '3']

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4) Extract Letters Only

From "abc123xyz", extract only the alphabetic letters.

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5) First Match Only

Use re.search() to find the first occurrence of any vowel (a,e,i,o,u) in "bcdfae" and print its position (index).

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6) Match at Start

Use re.match() to check if a string starts with "202".

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7) Validate Simple Email

Write a regex to check if an input string is a simple email containing letters, digits, @, and . (basic validation).

Example:

[e-mail]

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8) Find Words of Length √

From "one two three", find all words of exactly three letters.

Expected:

['one','two']

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9) Replace Digits

Replace all digits in "abc123xyz" with "*", then print the result.

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10) Split on Spaces

Take a sentence and split it into words using re.split() where spaces may be multiple.

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11) Check Numeric String

Ask for input and print True if the string contains only digits (no letters).

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12) Find Words Beginning With Capital

From "Hello World Python regex", extract words that start with a capital letter.

Expected:

['Hello','World','Python']

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13) Count Vowels

Use regex to find all vowels in a text and print the count.

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14) Strip Non-Alphanumeric

Given "@hello! Python#", remove anything that isn’t a letter or digit.

Requested output:

hello Python

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15) Find Repeated Characters

In "baalloon", find characters that repeat (like aa or ll).

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16) Extract Extensions

Given a list of filenames:

["file.txt","8data.csv","image.png"]

Extract the file extensions using regex.

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17) Validate Simple Phone Number

Validate if input matches:

xxx-xxx-xxxx

where x is a digit.

Example valid:

123-456-7890

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18) Find Words With Numbers

From "abc 123 def45 ghi", only extract tokens that contain at least one digit.

Expected:

['123','def45']

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19) Remove Extra Spaces

Given:

"  hello     world  "

use regex to reduce multiple spaces to a single space.

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20) Extract Time Format

From "The time is 12:45 pm", extract the time (12:45) using regex.

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🧠 Regex Concepts Practiced

Task Type	Example Pattern
Literal match	"hello"
Character classes	[a-z], \d
Word boundaries	\bword\b
Vowels	[aeiou]
Start of string	^pattern
End of string	pattern$
Repetition	+, *, {n}
Groups & extraction	(...)
Replace	re.sub()
Split	re.split()

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🧪 Python re Usage Template

Importing

import re

Match at start

if re.match("^hello", text):
    print("Starts with hello")

Search anywhere

res = re.search("\d+", text)

Find all

nums = re.findall("\d", text)

Replace

clean = re.sub("\d", "*", text)

Split

words = re.split("\s+", text)

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canvil: 333f6c7d-6876-4f7e-b6ad-1bdb2233f5c1