with open("source.txt", "w") as f:    f.write("apple\nbutter\ncherry\nmelon\ntea\n") with open("source.txt") as src, open("filtered.txt", "w") as dst:    for line in src:        if "t" not in line.lower():            dst.write(line)print(open("filtered.txt").read())

apple
cherry
melon

def permutations(text):    if len(text) <= 1:        return [text]    result = []    for i, ch in enumerate(text):        for rest in permutations(text[:i] + text[i + 1:]):            result.append(ch + rest)    return result print(permutations("abc"))

['abc', 'acb', 'bac', 'bca', 'cab', 'cba']

ONES = ["zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",        "ten", "eleven", "twelve", "thirteen", "fourteen", "fifteen", "sixteen",        "seventeen", "eighteen", "nineteen"]TENS = ["", "", "twenty", "thirty", "forty", "fifty", "sixty", "seventy", "eighty", "ninety"] def to_words(n):    if n < 20:        return ONES[n]    if n < 100:        return TENS[n // 10] + ("" if n % 10 == 0 else "-" + ONES[n % 10])    rest = n % 100    return ONES[n // 100] + " hundred" + ("" if rest == 0 else " and " + to_words(rest)) for n in [0, 15, 42, 305, 999]:    print(n, "->", to_words(n))

0 -> zero
15 -> fifteen
42 -> forty-two
305 -> three hundred and five
999 -> nine hundred and ninety-nine

import re def is_valid_mobile(number):    return bool(re.fullmatch(r"(\+91[\s-]?)?[6-9]\d{9}", number.strip())) for n in ["9876543210", "+91 9123456789", "12345", "5876543210"]:    print(n, is_valid_mobile(n))

9876543210 True
+91 9123456789 True
12345 False
5876543210 False

def last_word_length(text):    words = text.split()    return len(words[-1]) if words else 0 print(last_word_length("Learning Python is fun   "), last_word_length("   "))

3 0

def search(text, words):    found = set(text.lower().split())    return {w: w.lower() in found for w in words} print(search("Python makes testing easy", ["testing", "java", "easy"]))

{'testing': True, 'java': False, 'easy': True}

def add_binary(a, b):    return bin(int(a, 2) + int(b, 2))[2:] print(add_binary("1011", "111"))

10010

books = {} def add_book(title):    books[title] = True                # True means available def issue(title):    if books.get(title):        books[title] = False        return f"Issued '{title}'"    return f"'{title}' is not available" def return_book(title):    if title in books and not books[title]:        books[title] = True        return f"Returned '{title}'"    return f"'{title}' was not issued" def available():    return [t for t, ok in books.items() if ok] for t in ["Python Basics", "Clean Code", "Atomic Habits"]:    add_book(t)print(issue("Clean Code"))print(issue("Clean Code"))print(return_book("Clean Code"))print("Available:", available())

Issued 'Clean Code'
'Clean Code' is not available
Returned 'Clean Code'
Available: ['Python Basics', 'Clean Code', 'Atomic Habits']

def reverse_int(n):    sign = -1 if n < 0 else 1    return sign * int(str(abs(n))[::-1]) print(reverse_int(1234), reverse_int(-560))

4321 -65

def is_leap(year):    return year % 4 == 0 and (year % 100 != 0 or year % 400 == 0) print(is_leap(2024), is_leap(2100))

True False