import re text = "Order 4521 shipped on 2026-11-02, order 4522 pending"match = re.search(r"\d+", text)      # first run of digitsprint(match.group(), match.start(), match.end()) print(re.findall(r"\d+", text))     # every run of digits

4521 6 10
['4521', '2026', '11', '02', '4522']

import re print(re.match(r"\d+", "123abc"))print(re.match(r"\d+", "abc123"))print(bool(re.fullmatch(r"\d{6}", "411001")), bool(re.fullmatch(r"\d{6}", "41100")))print(re.sub(r"\s+", " ", "too    many   spaces"))print(re.split(r"[,;]\s*", "a, b;c ,d"))

<re.Match object; span=(0, 3), match='123'>
None
True False
too many spaces
['a', 'b', 'c ', 'd']

import re s = "Room B-12, floor 3; call +91 98765 43210"print(re.findall(r"[A-Z]", s))print(re.findall(r"[aeiou]", s))print(re.findall(r"[^\w\s]", s))

['R', 'B']
['o', 'o', 'o', 'o', 'a']
['-', ',', ';', '+']

import re print(re.findall(r"colou?r", "color colour colr"))print(re.findall(r"\d{2,3}", "1 12 123 1234"))print(re.findall(r"go+gle", "ggle gogle google gooogle"))

['color', 'colour']
['12', '123', '123']
['gogle', 'google', 'gooogle']

import re html = "<b>bold</b> and <i>italic</i>"print(re.findall(r"<.+>", html))     # greedy: one huge matchprint(re.findall(r"<.+?>", html))    # lazy: each tag

['<b>bold</b> and <i>italic</i>']
['<b>', '</b>', '<i>', '</i>']

import re print(re.findall(r"\bcat\b", "cat catalog concat cat."))print(bool(re.search(r"^ERROR", "ERROR: disk full")), bool(re.search(r"\.py$", "test_login.py")))

['cat', 'cat']
True True

import re log = "2026-11-02 ERROR db; 2026-11-03 WARN cache"for m in re.finditer(r"(\d{4})-(\d{2})-(\d{2}) (\w+)", log):    print(m.group(0), "->", m.group(1), m.group(4)) print(re.findall(r"(\d{4})-\d{2}-\d{2} (\w+)", log))

2026-11-02 ERROR -> 2026 ERROR
2026-11-03 WARN -> 2026 WARN
[('2026', 'ERROR'), ('2026', 'WARN')]

import re m = re.search(r"(?P<user>[\w.]+)@(?P<domain>[\w.-]+)", "contact: asha.k@sqatools.in today")print(m.group("user"), m.group("domain"))print(m.groupdict())

asha.k sqatools.in
{'user': 'asha.k', 'domain': 'sqatools.in'}

import reprint(re.sub(r"(\d{4})-(\d{2})-(\d{2})", r"\3/\2/\1", "Due 2026-11-02 and 2026-12-25"))

Due 02/11/2026 and 25/12/2026

import re text = "Python\npython\nPYTHON"print(re.findall(r"python", text, flags=re.IGNORECASE))print(re.findall(r"^p\w+", text, flags=re.I | re.M))     # ^ at every line start

['Python', 'python', 'PYTHON']
['Python', 'python', 'PYTHON']

import re EMAIL = re.compile(r"^[\w.+-]+@[\w-]+(\.[\w-]+)+$")for e in ["asha@sqatools.in", "bad@", "ravi.k+test@mail.co.uk", "no spaces@x.com"]:    print(e, bool(EMAIL.match(e)))

asha@sqatools.in True
bad@ False
ravi.k+test@mail.co.uk True
no spaces@x.com False

import re price = "Rs. 1,499.50 (incl. tax)"print(re.findall(r"\d[\d,]*\.\d+", price))print(re.escape("1+1=2?"))

['1,499.50']
1\+1=2\?

import mathprint(math.sqrt(81)) from math import pi, floorprint(round(pi, 4), floor(7.9)) import statistics as statsprint(stats.mean([4, 8, 15, 16, 23, 42]))

9.0
3.1416 7
18

import randomnames = [n for n in dir(random) if not n.startswith("_")]print(len(names) > 20)print("choice" in names, "shuffle" in names)print(random.choice.__doc__.splitlines()[0])

True
True True
Choose a random element from a non-empty sequence.

TAX_RATE = 0.18 def with_tax(amount):    return round(amount * (1 + TAX_RATE), 2) def discount(amount, percent):    return round(amount * (1 - percent / 100), 2)

import pricingfrom pricing import discount print(pricing.with_tax(1000))print(discount(1000, 15))print(pricing.TAX_RATE)

1180.0
850.0
0.18

def greet(name):    return f"Hello, {name}" print("__name__ is", __name__) if __name__ == "__main__":    print(greet("from the command line"))

__name__ is __main__
Hello, from the command line

import greeterprint(greeter.greet("from app.py"))

__name__ is greeter
Hello, from app.py

myshop/    __init__.py    pricing.py    cart.pymain.py          ->  from myshop.pricing import with_tax

$ python -m pip --versionpip 26.2.2 from C:\Python3\Lib\site-packages\pip (python 3.15)

$ python -m venv .venv$ .venv\Scripts\python -c "import sys; print(sys.prefix.endswith('.venv'))"True

class Shape:    def area(self):        raise NotImplementedError class Circle(Shape):    def __init__(self, r):        self.r = r    def area(self):        return round(3.14159 * self.r ** 2, 2) class Square(Shape):    def __init__(self, side):        self.side = side    def area(self):        return self.side ** 2 for shape in [Circle(1), Square(3), Circle(2)]:    print(type(shape).__name__, shape.area())

Circle 3.14
Square 9
Circle 12.57

class PdfReport:    def export(self):        return "report.pdf" class CsvReport:    def export(self):        return "report.csv" def save_all(reports):    for r in reports:        print("saved", r.export()) save_all([PdfReport(), CsvReport()])

saved report.pdf
saved report.csv

for thing in ["abc", [1, 2], {"a": 1}, range(10)]:    print(type(thing).__name__, len(thing))

str 3
list 2
dict 1
range 10

class Money:    def __init__(self, amount):        self.amount = amount     def __add__(self, other):        return Money(self.amount + other.amount)     def __lt__(self, other):        return self.amount < other.amount     def __repr__(self):        return f"Money({self.amount})" a, b = Money(250), Money(100)print(a + b)print(a < b, sorted([a, b]))

Money(350)
False [Money(100), Money(250)]

class Wallet:    def __init__(self):        self._currency = "INR"      # internal by convention        self.__balance = 0          # name-mangled     def add(self, amount):        self.__balance += amount     def balance(self):        return self.__balance w = Wallet()w.add(500)print(w.balance(), w._currency)print(w._Wallet__balance)          # still reachable if you insistprint(w.__balance)

500 INR
500
Traceback (most recent call last):
  File "main.py", line 16, in <module>
    print(w.__balance)
          ^^^^^^^^^^^
AttributeError: 'Wallet' object has no attribute '__balance'. Did you mean '.balance' instead of '.__balance'?

class Product:    def __init__(self, name, price):        self.name = name        self.price = price          # goes through the setter below     @property    def price(self):        return self._price     @price.setter    def price(self, value):        if value < 0:            raise ValueError("price cannot be negative")        self._price = value     @property    def price_with_tax(self):       # read-only computed attribute        return round(self._price * 1.18, 2) p = Product("Mouse", 349)p.price = 399print(p.price, p.price_with_tax) try:    p.price = -5except ValueError as e:    print("Error:", e)

399 470.82
Error: price cannot be negative

class Vehicle:    def __init__(self, brand):        self.brand = brand     def start(self):        return f"{self.brand} engine started" class Car(Vehicle):        # Car inherits from Vehicle    pass c = Car("Tata")print(c.start())print(isinstance(c, Car), isinstance(c, Vehicle))

Tata engine started
True True

class Vehicle:    def __init__(self, brand):        self.brand = brand class Car(Vehicle):    def __init__(self, brand, seats):        super().__init__(brand)     # let Vehicle set brand        self.seats = seats          # then add Car's own data c = Car("Mahindra", 7)print(c.brand, c.seats)

Mahindra 7

class Employee:    def __init__(self, name, salary):        self.name = name        self.salary = salary     def annual_pay(self):        return self.salary * 12     def describe(self):        return f"{self.name} earns {self.annual_pay()} a year" class Manager(Employee):    def __init__(self, name, salary, bonus):        super().__init__(name, salary)        self.bonus = bonus     def annual_pay(self):                     # override        return super().annual_pay() + self.bonus staff = [Employee("Asha", 50000), Manager("Ravi", 80000, 100000)]for person in staff:    print(person.describe())

Asha earns 600000 a year
Ravi earns 1060000 a year

class BasePage:    url = "/"     def __init__(self, base_url):        self.base_url = base_url     def open(self):        return f"GET {self.base_url}{self.url}" class LoginPage(BasePage):    url = "/login"     def login(self, user):        return f"{self.open()} -> sign in as {user}" class CartPage(BasePage):    url = "/cart" print(LoginPage("https://shop.test").login("asha"))print(CartPage("https://shop.test").open())

GET https://shop.test/login -> sign in as asha
GET https://shop.test/cart

class Animal:    def breathe(self):        return "breathing" class Mammal(Animal):    def feed(self):        return "feeding milk" class Dog(Mammal):    def bark(self):        return "woof" d = Dog()print(d.breathe(), "|", d.feed(), "|", d.bark())

breathing | feeding milk | woof

class Flyer:    def move(self):        return "flying" class Swimmer:    def move(self):        return "swimming" class Duck(Flyer, Swimmer):    pass print(Duck().move())print([cls.__name__ for cls in Duck.__mro__])

flying
['Duck', 'Flyer', 'Swimmer', 'object']

class A: passclass B(A): pass print(issubclass(B, A), issubclass(A, B))print(isinstance(B(), A))

True False
True

from abc import ABC, abstractmethod class Shape(ABC):    @abstractmethod    def area(self):        ... class Square(Shape):    def __init__(self, side):        self.side = side    def area(self):        return self.side ** 2 print(Square(4).area())Shape()

16
Traceback (most recent call last):
  File "main.py", line 15, in <module>
    Shape()
    ~~~~~^^
TypeError: Can't instantiate abstract class Shape without an implementation for abstract method 'area'

colors = ["red", "green", "blue"]it = iter(colors) print(next(it))print(next(it))print(next(it))

red
green
blue

it = iter([1])print(next(it))print(next(it))

1
Traceback (most recent call last):
  File "main.py", line 3, in <module>
    print(next(it))
          ~~~~^^^^
StopIteration

it = iter([])print(next(it, "no more items"))

no more items

items = ["a", "b", "c"] it = iter(items)while True:    try:        item = next(it)    except StopIteration:        break    print(item)

a
b
c

squares = map(lambda x: x * x, [1, 2, 3])    # map returns an iteratorprint(list(squares))print(list(squares))      # already used up nums = [1, 2, 3]print(sum(nums), sum(nums))   # a list gives a new iterator each time

[1, 4, 9]
[]
6 6

class Countdown:    def __init__(self, start):        self.current = start     def __iter__(self):        return self     def __next__(self):        if self.current <= 0:            raise StopIteration        value = self.current        self.current -= 1        return value for n in Countdown(3):    print(n)print(list(Countdown(5)))

3
2
1
[5, 4, 3, 2, 1]

import itertools counter = itertools.count(start=100, step=10)print([next(counter) for _ in range(3)]) print(list(itertools.islice(itertools.cycle("AB"), 5)))print(list(itertools.chain([1, 2], (3, 4), "56")))print(list(itertools.combinations("ABC", 2)))print(list(itertools.product([0, 1], repeat=2)))

[100, 110, 120]
['A', 'B', 'A', 'B', 'A']
[1, 2, 3, 4, '5', '6']
[('A', 'B'), ('A', 'C'), ('B', 'C')]
[(0, 0), (0, 1), (1, 0), (1, 1)]

pairs = zip(["a", "b", "c"], [1, 2, 3])print(next(pairs))print(list(pairs))       # continues from where next() left off

('a', 1)
[('b', 2), ('c', 3)]