Python Cheat Sheet (Quick Reference)

You don't need to memorize every method name to write Python. Professional developers look things up all the time. This Python cheat sheet puts the syntax you use most on one page, in short tables and code snippets, so you can find what you need in seconds. Every section links to the full lesson if you want the details.

Syntax basics and data types

# A comment starts with #
name = "Ava"            # str
age = 29                # int
height = 1.68           # float
is_member = True        # bool
nothing = None          # no value

x, y = 3, 4             # multiple assignment
x, y = y, x             # swap
MAX_USERS = 100         # constant by convention

if age >= 18:           # a colon starts a block
    print("Adult")      # blocks are indented 4 spaces

Convert types with int("5"), float("2.5"), str(10), list("abc"); check them with type(x) or isinstance(x, int). Read input with input("Prompt: ") (always returns a string). Full lessons: syntax, variables, data types, type conversion.

Operators

Precedence from high to low: **, then * / // %, then + -, then comparisons, then not, and, or. When in doubt, use parentheses. See arithmetic operators and operator precedence.

Strings and f-string formatting

s = "Hello, World"
print(s[0], s[-1], s[0:5], s[::-1])
print(len(s), s.upper(), s.lower())
print(s.replace("World", "Python"))
print(s.split(", "))
print("-".join(["a", "b", "c"]))

H d Hello dlroW ,olleH
12 HELLO, WORLD hello, world
Hello, Python
['Hello', 'World']
a-b-c

f-string formats:

price, item, n = 1234.5, "tea", 7
print(f"{price:.2f}")      # 2 decimal places
print(f"{price:,.2f}")     # thousands separator
print(f"{0.256:.1%}")      # percentage
print(f"{n:03d}")          # pad with zeros
print(f"[{item:>6}]")      # right-align in 6 characters
print(f"{item=}")          # name and value, for debugging

1234.50
1,234.50
25.6%
007
[   tea]
item='tea'

Escape characters: \n new line, \t tab, \\ backslash, \" quote. Full lessons: strings, slicing, string methods, f-strings, escape characters.

Lists, tuples, sets and dictionaries

cart = ["milk", "eggs"]
cart.append("bread")
cart.insert(0, "apples")
cart.remove("eggs")
print(cart, len(cart))

point = (3, 4)                 # tuple: fixed
x, y = point                   # unpacking

tags = {"red", "blue"}         # set: unique items
tags.add("red")
print(sorted(tags))

user = {"name": "Ava", "age": 29}
user["city"] = "Lisbon"        # add or update
print(user.get("email", "n/a"))
for key, value in user.items():
    print(key, value)

['apples', 'milk', 'bread'] 3
['blue', 'red']
n/a
name Ava
age 29
city Lisbon

Full lessons: list methods, tuples, sets, dictionary methods, which one to use.

Control flow

temp = 23
if temp > 30:
    print("Hot")
elif temp > 15:
    print("Mild")
else:
    print("Cold")

label = "even" if temp % 2 == 0 else "odd"   # one-line if

for i in range(1, 3):           # 1, 2 (stop is excluded)
    print("Round", i)

for i, fruit in enumerate(["kiwi", "fig"], start=1):
    print(i, fruit)

count = 3
while count > 0:
    count -= 1
    if count == 1:
        continue                # skip the rest of this round
    print("count", count)

Mild
Round 1
Round 2
1 kiwi
2 fig
count 2
count 0

Also: break leaves a loop, pass does nothing, range(start, stop, step) never includes stop, and match/case compares one value against several patterns. Full lessons: if-else, match-case, for loop, while loop, break, continue, pass.

Functions and comprehensions

def greet(name, greeting="Hello"):     # default argument
    """Return a friendly greeting."""  # docstring
    return f"{greeting}, {name}!"

print(greet("Leo"))
print(greet("Leo", greeting="Hi"))     # keyword argument

def total(*prices, **options):         # any number of arguments
    return sum(prices) * (1 - options.get("discount", 0))

print(total(10, 20, discount=0.1))

square = lambda n: n * n               # small anonymous function
print(square(5))

nums = [1, 2, 3, 4, 5]
print([n * 2 for n in nums if n % 2])         # list comprehension
print({n: n * n for n in nums[:3]})           # dict comprehension
print({len(w) for w in ["hi", "yo", "hey"]})  # set comprehension

Hello, Leo!
Hi, Leo!
27.0
25
[2, 6, 10]
{1: 1, 2: 4, 3: 9}
{2, 3}

Scope follows the LEGB rule (Local, Enclosing, Global, Built-in). Full lessons: functions, *args and **kwargs, scope, lambda, comprehensions.

Exceptions and files

try:
    amount = int("12a")
except ValueError as error:
    print("Bad number:", error)
else:
    print("Parsed!")          # only if no error
finally:
    print("Always runs")

def withdraw(balance, amount):
    if amount > balance:
        raise ValueError("Insufficient funds")
    return balance - amount

Bad number: invalid literal for int() with base 10: '12a'
Always runs

with open("notes.txt", "w", encoding="utf-8") as f:
    f.write("First line\n")

with open("notes.txt", encoding="utf-8") as f:
    for line in f:
        print(line.strip())

First line

Common errors: NameError, TypeError, ValueError, KeyError, IndexError, ZeroDivisionError, FileNotFoundError. Full lessons: try-except, raise, reading files, writing files, JSON, pathlib.

Classes

class Pet:
    species = "animal"                  # class attribute

    def __init__(self, name):
        self.name = name                # instance attribute

    def speak(self):
        return "..."

    def __str__(self):
        return f"{self.name} the {self.species}"

class Dog(Pet):                         # inheritance
    species = "dog"

    def speak(self):                    # override
        return "Woof!"

rex = Dog("Rex")
print(rex, "-", rex.speak())
print(isinstance(rex, Pet))

Rex the dog - Woof!
True

from dataclasses import dataclass

@dataclass
class Point:
    x: int
    y: int = 0

print(Point(3))

Point(x=3, y=0)

Also: super().__init__(...) calls the parent's constructor, @classmethod receives cls, @staticmethod receives nothing, and a leading underscore (_balance) marks an attribute as internal. Full lessons: classes and objects, inheritance, magic methods, dataclasses.

Built-in functions and useful modules

Install third-party packages with pip install package-name, ideally inside a virtual environment. Full lessons: built-in functions, modules, math and random, datetime, pip and virtual environments, regex.

Common mistakes to double-check

Practice exercise

orders = [("latte", 4.5), ("muffin", 3.25), ("latte", 4.5), ("tea", 2.0)]

counts = {}
for item, price in orders:
    counts[item] = counts.get(item, 0) + 1

revenue = sum(price for item, price in orders)
print(counts)
print(f"Revenue: ${revenue:.2f}")

{'latte': 2, 'muffin': 1, 'tea': 1}
Revenue: $14.25

Congratulations: you've completed the Python tutorial!

🎉 You made it to the end. You started with your first print() call and now you can work with data structures, write functions and classes, handle errors, read and write files, and build complete projects. That's a real foundation, and every Python library you'll use next is built on exactly these ideas.

Here's how to keep the momentum going:

• Test what you remember with the practice quizzes.
• Revisit the Python exercises and interview questions in a week; you'll be surprised how much easier they feel.
• Build something of your own: a habit tracker, a budget script or a tiny game. Real projects teach you the most.
• Explore more topics in our other tutorials.

Thanks for learning with us, and happy coding!