Output & variables→
print("Hallo")- Print text
x = 5- Store a value in a variable
f"{name} ist {alter}"- f-string: put variables into text
name = input("Name? ")- Read input (always text!)
int("12") float("2.5") str(7)- Convert type
Quick reference
Python cheat sheet
Everything important on one page. Tip: press Ctrl+P (Mac: ⌘+P) to print it.
Maths & comparing
+ - * /- Basic arithmetic
// % **- floor division · remainder · power
== != < > <= >=- Comparisons → True/False
and or not- Combine conditions
x += 1- Increase x by 1
Decisions→
if x > 10: ... elif x > 5: ... else: ...- The first matching branch runs
Loops→
for i in range(5):- 0, 1, 2, 3, 4
range(1, 10, 2)- start, end (excluded), step
while x < 100:- Repeat while true
break continue- Leave loop · next round
for i, w in enumerate(items):- Loop with a counter
Lists→
l = [3, 1, 2]- Create a list
l[0] l[-1] l[1:3]- first · last · slice
l.append(4) l.remove(1) l.pop()- append · remove · take out the last
len(l) sum(l) max(l) min(l)- length · sum · largest · smallest
sorted(l) 3 in l- sorted · contained?
Strings→
s.upper() s.lower() s.strip()- upper · lower · trim spaces
s.replace("a", "b") s.split(",")- replace · split
"-".join(items)- join a list into text
s[::-1] len(s) s.count('e')- reversed · length · count
Dictionaries→
d = {"Mia": 2, "Ben": 1}- key: value
d["Mia"] d.get("Tom", 0)- look up · look up safely
d["Lea"] = 3- add or change
for k, v in d.items():- go through all pairs
Functions→
def f(x, y=2): return x * y- Function with a default value
f(3) f(3, 5)- call it
lambda x: x * 2- One-line mini function
Handling errors→
try: ... except ValueError: ...- Catch errors instead of crashing
assert x > 0, 'Text'- Check – otherwise AssertionError
Files & modules→
with open("a.txt", "w") as f: f.write("Hi\n")- write ('a' = append)
for line in open("a.txt"):- read line by line
import math from random import randint- import modules
Classes→
class Robo: def __init__(self, name): self.name = name def hello(self): return self.name- Blueprint with attribute and method
r = Robo("R2") r.hello()- Build and use an object
Pro→
[x * 2 for x in l if x > 0]- List comprehension with filter
{k: len(k) for k in words}- Dictionary comprehension
def gen(): yield 1- Generator
@decorator def f(): ...- Extend a function
def f(x: int) -> str:- Type hints
async def f(): await asyncio.sleep(1)- Coroutine
Pybricks (LEGO SPIKE)
hub = PrimeHub()- create the hub
hub.light.on(Color.RED) hub.display.text("Hi")- light · scrolling text
drive_base = DriveBase(l, r, wheel_diameter=56, axle_track=114)- two motors as a drive base
drive_base.straight(200) drive_base.turn(90)- drive (mm) · turn (degrees)
sensor.distance() color.reflection()- distance in mm · brightness 0–100
wait(500)- wait 500 ms