Create a table

Write a Python program to create a SQLite table and list the tables in the database.

[('students',)]

Approach

1. CREATE TABLE, then query sqlite_master.

Solution

import sqlite3 conn = sqlite3.connect(":memory:")conn.execute("CREATE TABLE students (id INTEGER PRIMARY KEY, name TEXT NOT NULL, marks INTEGER)")print(conn.execute("SELECT name FROM sqlite_master WHERE type = 'table'").fetchall())

[('students',)]

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Match positions with finditer

Write a Python program to print each match of a word with its start and end positions.

python (0, 6)
pytest (11, 17)
pyodide (22, 29)

Approach

1. finditer gives match objects with span().

Solution

import re for m in re.finditer(r"py\w*", "python and pytest use pyodide"):    print(m.group(), m.span())

python (0, 6)
pytest (11, 17)
pyodide (22, 29)

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Multiline and ignore-case flags

Write a Python program to find lines that start with “error” in any case.

['Error: disk full', 'ERROR: timeout']

Approach

1. re.M makes ^ match at every line start; re.I ignores case.

Solution

import re log = "Error: disk full\ninfo: ok\nERROR: timeout\nwarning: slow"print(re.findall(r"^error:.*$", log, flags=re.M | re.I))

['Error: disk full', 'ERROR: timeout']

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Extract prices

Write a Python program to extract rupee prices like Rs 1,499.50 and add them up.

[349.0, 1499.5, 99.0] 1947.5

Approach

1. Capture the number, remove commas, convert.

Solution

import re text = "Mouse Rs 349, keyboard Rs 1,499.50, cable Rs 99"prices = [float(p.replace(",", "")) for p in re.findall(r"Rs\s?([\d,]+(?:\.\d+)?)", text)]print(prices, sum(prices))

[349.0, 1499.5, 99.0] 1947.5

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Find repeated words

Write a Python program to find accidentally repeated words like “the the”.

['is', 'the', 'module']
This is a test of the regex module.

Approach

1. A back-reference \1 matches the same text again.

Solution

import re text = "This is is a test of the the regex module module."print(re.findall(r"\b(\w+)\s+\1\b", text))print(re.sub(r"\b(\w+)\s+\1\b", r"\1", text))

['is', 'the', 'module']
This is a test of the regex module.

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camelCase to snake_case

Write a Python program to convert camelCase names to snake_case.

firstName -> first_name
getHTTPResponse -> get_httpresponse
userIdNumber -> user_id_number

Approach

1. Insert “_” before each capital, then lower-case.

Solution

import re for name in ["firstName", "getHTTPResponse", "userIdNumber"]:    print(name, "->", re.sub(r"(?<=[a-z0-9])(?=[A-Z])", "_", name).lower())

firstName -> first_name
getHTTPResponse -> get_httpresponse
userIdNumber -> user_id_number

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Validate an IPv4 address

Write a Python program to check IPv4 addresses (each part 0-255).

192.168.1.10 True
256.1.1.1 False
10.0.0 False
8.8.8.8 True

Approach

1. Use regex for the shape and Python for the range.

Solution

import re def is_ipv4(text):    if not re.fullmatch(r"\d{1,3}(\.\d{1,3}){3}", text):        return False    return all(0 <= int(part) <= 255 for part in text.split(".")) for ip in ["192.168.1.10", "256.1.1.1", "10.0.0", "8.8.8.8"]:    print(ip, is_ipv4(ip))

192.168.1.10 True
256.1.1.1 False
10.0.0 False
8.8.8.8 True

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Mask card numbers

Write a Python program to mask all but the last 4 digits of card numbers.

Card XXXX-XXXX-XXXX-1234 and XXXX-XXXX-XXXX-9876

Approach

1. Capture the last 4 digits and replace the rest.

Solution

import re text = "Card 4111 1111 1111 1234 and 5500-0000-0000-9876"print(re.sub(r"\d{4}[ -]\d{4}[ -]\d{4}[ -](\d{4})", r"XXXX-XXXX-XXXX-\1", text))

Card XXXX-XXXX-XXXX-1234 and XXXX-XXXX-XXXX-9876

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Parse log lines with named groups

Write a Python program to parse “LEVEL date message” log lines into dictionaries.

{'level': 'ERROR', 'date': '2026-11-02', 'msg': 'db timeout'}
{'level': 'INFO', 'date': '2026-11-02', 'msg': 'started'}

Approach

1. Named groups and groupdict().

Solution

import re LINE = re.compile(r"(?P<level>[A-Z]+) (?P<date>\d{4}-\d{2}-\d{2}) (?P<msg>.+)")for line in ["ERROR 2026-11-02 db timeout", "INFO 2026-11-02 started"]:    print(LINE.match(line).groupdict())

{'level': 'ERROR', 'date': '2026-11-02', 'msg': 'db timeout'}
{'level': 'INFO', 'date': '2026-11-02', 'msg': 'started'}

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Match whole words only

Write a Python program to count the word “test” but not “testing” or “latest”.

2 3

Approach

1. \btest\b.

Solution

import re text = "test testing latest test. Test"print(len(re.findall(r"\btest\b", text)), len(re.findall(r"\btest\b", text, re.I)))

2 3

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