Python cheat sheet
Core Python 3 syntax for quick lookup.
Basics
x = 5- Assign a value (no declaration needed)
print(f"Total: {x * 2}")- Print with an f-string
7 // 2 7 % 2 2 ** 3- Floor division, remainder, power
int("42") float("3.5") str(7)- Convert types
type(x)- Show the type of a value
input("Name: ")- Read text from the user
Strings
s.upper() s.lower()- Change case
s.strip()- Remove spaces at both ends
s.split(",")- Split into a list
",".join(items)- Join a list into a string
s.replace("a", "b")- Replace text
s[0] s[-1] s[1:4]- First, last, slice
Lists
items = [1, 2, 3]- Create a list
items.append(4)- Add to the end
items.pop()- Remove and return the last item
len(items)- Number of items
sorted(items, reverse=True)- New sorted list, descending
[n * 2 for n in items if n > 1]- List comprehension
Dictionaries
d = {"a": 1}- Create a dictionary
d["b"] = 2- Add or change a key
d.get("c", 0)- Read with a default
for k, v in d.items():- Loop over keys and values
"a" in d- Check a key
Control flow
if x > 0: elif x == 0: else:- Decisions (indent the block)
for i in range(3):- Loop 0, 1, 2
while cond:- Loop while true
break continue- Leave the loop, skip a round
def f(a, b=1): return a + b- Define a function
Files and errors
with open("f.txt", encoding="utf-8") as f:- Open a file safely
f.read() f.readlines()- Whole text, list of lines
open("f.txt", "w")- Write mode (erases the file first)
try: ... except ValueError: ...- Handle a specific error
python3 -m venv .venv- Create a virtual environment
pip install <package>- Install a package
Learn it properly