Python Cheat Sheets

print("Hello, World!")

print(type(3.14))  # <class "float">
print(isinstance("a", str))  # True

int("5")  # 5
float("3.14")  # 3.14
str(5)  # "5"
list("abc")  # ["a","b","c"]

[x*x for x in range(5)]  # [0, 1, 4, 9, 16]

[x for x in range(10) if x % 2 == 0]  # [0, 2, 4, 6, 8]

matrix = [[1,2],[3,4]]
flattened = [num for row in matrix for num in row]  # [1,2,3,4]

x = 10
if x > 5:
    print("Greater")
elif x == 5:
    print("Equal")
else:
    print("Smaller")

for i in range(3):
    print(i)

for i in [1,2,3]:
    print(i)

i = 0
while i < 3:
    print(i)
    i += 1

def add(a, b):
    return a + b

def greet(name="World"):
    print(f"Hello, {name}")

def func(*args, **kwargs):
    print(args)
    print(kwargs)

square = lambda x: x * x
print(square(5))  # 25

nums = [1, 2, 3]
squares = list(map(lambda x: x*x, nums))

nums = [1, 2, 3, 4]
evens = list(filter(lambda x: x % 2 == 0, nums))

from functools import reduce
nums = [1, 2, 3, 4]
product = reduce(lambda x, y: x * y, nums)

class Car:
    def __init__(self, brand):
        self.brand = brand
    def start(self):
        print(f"{self.brand} is starting")

class Animal:
    def speak(self):
        print("Animal speaks")

class Dog(Animal):
    def speak(self):
        print("Woof!")

class Example:
    @staticmethod
    def static():
        print("Static method")
    @classmethod
    def cls(cls):
        print("Class method")

def my_decorator(func):
    def wrapper():
        print("Before")
        func()
        print("After")
    return wrapper

@my_decorator
def greet():
    print("Hello!")

def counter():
    for i in range(3):
        yield i

it = iter([1,2,3])
print(next(it))  # 1

def counter():
    for i in range(3):
        yield i

try:
    x = 1 / 0
except ZeroDivisionError as e:
    print("Error:", e)

try:
    x = 1
except:
    pass
else:
    print("No error!")
finally:
    print("Always runs")

with open("file.txt", "r") as f:
    content = f.read()

with open("file.txt", "w") as f:
    f.write("Hello!")

with open("file.txt") as f:
    for line in f:
        print(line.strip())

import math
print(math.sqrt(16))

import random
print(random.randint(1, 100))

python -m venv venv
source venv/bin/activate

import unittest

class TestAdd(unittest.TestCase):
    def test_add(self):
        self.assertEqual(add(2, 3), 5)

if __name__ == "__main__":
    unittest.main()

def add(a: int, b: int) -> int:
    return a + b

from dataclasses import dataclass

@dataclass
class Point:
    x: int
    y: int

from pathlib import Path
p = Path("file.txt")
print(p.exists())

import logging
logging.basicConfig(level=logging.INFO)
logging.info("This is an info message")

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("--foo")
args = parser.parse_args()

import asyncio

async def main():
    print("Hello")
    await asyncio.sleep(1)
    print("World")

asyncio.run(main())

with open("file.txt") as f:
    data = f.read()

from contextlib import contextmanager

@contextmanager
def my_cm():
    print("Enter")
    yield
    print("Exit")

with my_cm():
    print("Inside")