Python Quick Reference

x = 10

a, b = 1, 2

a, b = b, a

print("Hello")

print("Loading", end="")

name = input("Name: ")

# this is a comment

type(x)

isinstance(x, int)

7 // 2   # 3

7 % 2    # 1

2 ** 10  # 1024

round(3.14159, 2)

math.floor(x)

math.ceil(x)

int("42")

float("3.5")

str(42)

min(nums)

max(nums)

sum(nums)

abs(-5)

f"Hi {name}, you are {age}"

f"{price:.2f}"

f"{n:,}"

len(text)

text.upper()

text.lower()

text.title()

text.strip()

text.lstrip()

text.rstrip()

text.replace("old", "new")

text.split(",")

", ".join(words)

"py" in text

text.find("py")

text.startswith("http")

text.endswith(".py")

text[0:3]

text[-3:]

text[::-1]  # reversed

"""line one
line two"""

nums = [3, 1, 2]

nums[0]

nums[-1]

nums.append(4)

nums.extend([5, 6])

nums.insert(0, 9)

nums.remove(2)

nums.pop()

nums.pop(0)

del nums[1]

nums.sort()

sorted(nums)

sorted(nums, reverse=True)

sorted(users, key=lambda u: u.age)

nums.reverse()

nums[::-1]

nums.index(3)

nums[1:3]

[n * 2 for n in nums if n > 1]

for i, n in enumerate(nums):

for a, b in zip(xs, ys):

point = (4, 5)

x, y = point

tags = {"a", "b"}

unique = list(set(items))

tags.add("c")

tags.discard("a")

a | b

a & b

a - b

user = {"name": "Ada", "age": 36}

user["name"]

user.get("email", "n/a")

user["email"] = "ada@example.com"

del user["age"]

user.pop("age", None)

"name" in user

for key, value in user.items():

user.keys()

user.values()

merged = a | b

a.update(b)

{k: v * 2 for k, v in prices.items()}

from collections import Counter
Counter(words).most_common(3)

from collections import defaultdict
groups = defaultdict(list)

if x > 0:
    ...
elif x == 0:
    ...
else:
    ...

label = "even" if n % 2 == 0 else "odd"

for i in range(5):

for i in range(1, 10, 2):

while count < 10:
    count += 1

break

continue

match command:
    case "start":
        run()
    case _:
        help()

any(n < 0 for n in nums)

all(n > 0 for n in nums)

def greet(name):
    return f"Hello, {name}"

def greet(name="world"):

greet(name="Ada")

def total(*nums, **options):

def add(a: int, b: int) -> int:

square = lambda n: n * n

list(map(str, nums))

list(filter(None, items))

class Dog:
    def __init__(self, name):
        self.name = name

    def bark(self):
        return "Woof"

rex = Dog("Rex")

class Puppy(Dog):
    def bark(self):
        return super().bark() + "!"

from dataclasses import dataclass

@dataclass
class Point:
    x: int
    y: int

def __repr__(self):
    return f"Dog({self.name!r})"

@property
def area(self):
    return self.w * self.h

try:
    value = int(text)
except ValueError as e:
    print(e)
finally:
    cleanup()

raise ValueError("bad input")

with open("data.txt") as f:
    text = f.read()

with open("data.txt") as f:
    for line in f:
        print(line.rstrip())

with open("out.txt", "w") as f:
    f.write("hello\n")

import json
data = json.loads(text)

json.dumps(data, indent=2)

from pathlib import Path
Path("logs").mkdir(exist_ok=True)

import math

from math import sqrt

import numpy as np

if __name__ == "__main__":
    main()

python -m venv .venv

source .venv/bin/activate   # macOS/Linux

.venv\Scripts\activate     # Windows

pip install requests

pip install -r requirements.txt

from datetime import datetime
datetime.now().isoformat()

import random
random.randint(1, 6)

random.choice(items)