Python Cheatsheet — Complete Quick Reference

x = 10            # int (dynamic typing)
y = 3.14          # float
name = "Python"   # str
is_ok = True      # bool

s = f"Hello {name}"     # f-string (3.6+)
s.upper(); s.lower(); s.strip()
s.split(","); ",".join(["a","b"])
s.startswith("H"); s.find("P")

nums = [1, 2, 3]
nums.append(4); nums.pop(); nums.sort()
nums[0]; nums[-1]; nums[1:3]  # slice
[x*2 for x in nums]           # list comprehension

d = {"a": 1, "b": 2}
d.get("c", 0); d.keys(); d.values(); d.items()
for k, v in d.items(): ...

t = (1, 2)          # immutable
s = {1, 2, 2, 3}    # {1, 2, 3} — duplicates removed
s.add(4); s.remove(1); s & {2, 3}; s | {4, 5}

if x > 0: ...
elif x == 0: ...
else: ...

for i in range(5): ...
while x > 0: ...

# match-case (3.10+)
match status:
    case 200: ...
    case _: ...

def add(a, b=0): return a + b
f = lambda x: x * 2
# *args, **kwargs
def log(*args, **kwargs): ...

class Dog:
    species = "Canine"                 # class var
    def __init__(self, name):          # constructor
        self.name = name               # instance var
    def bark(self): return f"{self.name} says woof"

with open("file.txt", "r") as f:
    content = f.read()          # str
    lines = f.readlines()       # list[str]
# Modes: r, w, a, r+, rb, wb

try:
    x = 1 / 0
except ZeroDivisionError:
    print("can't divide by zero")
except Exception as e:
    print(e)
finally:
    cleanup()

import math; math.sqrt(16)
from os import path; path.join("a","b")
from collections import defaultdict, Counter

[x*2 for x in range(10) if x % 2 == 0]      # list
{k: v*2 for k, v in d.items()}               # dict
{x for x in nums if x > 0}                   # set