Python cheat sheet

Variables, numbers and printing

Run ▸name = "Ada"          # str
age = 36              # int
height = 1.65         # float
is_coder = True       # bool

print(name, age)
print(f"{name} is {age} years old")   # f-string
print(7 / 2, 7 // 2, 7 % 2, 2 ** 10)  # 3.5 3 1 1024
age += 1                               # same as age = age + 1
print(type(height), int("42"), float("2.5"), str(99))

Strings

Input

Run ▸name = input("Name: ")            # always returns a string
age = int(input("Age: "))         # convert to a number
print(f"Hi {name}, next year you'll be {age + 1}")

Lists

Run ▸nums = [3, 1, 4, 1, 5]
nums.append(9)           # add to the end
nums.insert(0, 2)        # insert at index 0
nums.remove(1)           # remove first 1
last = nums.pop()        # remove and return last item
print(nums, last)        # [2, 3, 4, 1, 5] 9
print(sorted(nums), sum(nums), max(nums), len(nums))
print(nums[1:3], nums[-2:])
squares = [n * n for n in range(5)]          # comprehension
evens = [n for n in nums if n % 2 == 0]
print(squares, evens)

Dictionaries, sets and tuples

Run ▸ages = {"ann": 31, "bob": 25}
ages["cy"] = 40                   # add / update
print(ages.get("dan", "unknown")) # safe lookup
for name, age in ages.items():
    print(name, age)
del ages["bob"]
print(list(ages.keys()), "ann" in ages)

colors = {"red", "green", "red"}  # set: unique items
print(colors, len(colors))
point = (3, 4)                    # tuple: fixed
x, y = point                      # unpacking
print(x + y)

Conditions

Run ▸score = 72
if score >= 90:
    grade = "A"
elif score >= 70:
    grade = "B"
else:
    grade = "C"
print(grade)

# comparison: == != < <= > >=   logic: and or not   membership: in
label = "pass" if score >= 50 else "fail"   # one-line if
print(label, 0 < score < 100, not False)

Loops

Run ▸for i in range(3):              # 0 1 2
    print("i =", i)
for i, fruit in enumerate(["apple", "fig"], start=1):
    print(i, fruit)
for a, b in zip([1, 2], ["x", "y"]):
    print(a, b)

n = 3
while n > 0:
    print(n)
    n -= 1

for x in range(10):
    if x == 2:
        continue                # skip the rest of this pass
    if x == 4:
        break                   # leave the loop
    print("x", x)

Functions

Run ▸def area(width, height=1):
    """Return the area of a rectangle."""
    return width * height

print(area(3, 4), area(5), area(height=2, width=6))

def total(*numbers, **options):
    result = sum(numbers)
    return round(result, options.get("digits", 0))

print(total(1.5, 2.25, digits=1))
double = lambda x: x * 2
print(list(map(double, [1, 2, 3])))

Classes

Run ▸class Pet:
    def __init__(self, name, sound):
        self.name = name
        self.sound = sound

    def speak(self):
        return f"{self.name} says {self.sound}"

class Dog(Pet):                     # inheritance
    def __init__(self, name):
        super().__init__(name, "woof")

print(Dog("Rex").speak())

Errors and exceptions

Run ▸try:
    value = int("abc")
except ValueError as err:
    print("Not a number:", err)
else:
    print("no error")
finally:
    print("always runs")

Files and modules

Run ▸with open("notes.txt", "w") as f:      # "w" write, "a" append, "r" read
    f.write("line one\nline two\n")

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

import math, random
from datetime import date
print(math.sqrt(16), math.pi)
print(random.randint(1, 6) in range(1, 7))
print(date(2026, 1, 1).year)

Practise each section with the auto-checked exercises, and keep the syntax checker handy for typos.

Practise on your phone too

Python Coding - Learn Python for Android: a real Python 3 interpreter, code editor, 26 example programs and 12 marked exercises.

Get it on Google Play

Frequently asked questions

Keep going

Published 2026-10-22 · Updated 2026-10-22 · by the Coding Python team · code tested on Python 3