A beginner Python cheat sheet is the REPL and a .py file: assignment, types you can print, if/for, and def. Run python hello.py. Do not start with machine learning notebooks until you can write a loop and a function without copying.
This Python cheat sheet is written for people searching for a fast, accurate reference: students, junior developers, and teams shipping production software. Pin it, copy the snippets, and come back when syntax slips.
Quick reference
- Run:
python hello.pyorpy hello.pyon Windows. REPL:pythonthen expressions. - Print:
print("hi"). Commas add spaces.end=""to skip newline. - Variables:
name = "Ada",n = 3. Names are snake_case. - if:
if n > 0:elif/else. Colon and indent. - for:
for item in items:andfor i in range(5):. - while:
while n > 0:plusbreak/continue. Avoid infinite loops. - def:
def add(a, b): return a + b. - input:
input("Name: ")returns a string — wrapint(...)for numbers and catchValueError.
Copy-paste examples
First script: total a list of prices
Save as total.py and run it. Convert input with int only after you know it is digits.
def total(prices: list[int]) -> int:
s = 0
for p in prices:
s += p
return s
raw = input('Prices separated by commas: ')
parts = [p.strip() for p in raw.split(',') if p.strip()]
nums = [int(p) for p in parts]
print('Sum =', total(nums))Common mistakes
- Copy-pasting Jupyter cells without understanding
def. - Comparing strings and numbers (
"3" == 3is False) afterinput. - Using tabs in one file and spaces in another.
- Naming a file
random.pyand shadowing the standard library.
FAQ
- Do I need an IDE? Helpful (VS Code, PyCharm). Not required. A terminal and a text editor work.
- Python 3 or 2? Python 3 only. Ignore tutorials that
printwithout parentheses as a statement.
- When do I learn Django/Flask? After functions, virtualenv, and pip. Then a tiny Flask route or Django tutorial — not both at once.
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