Python

Variables and Data Types

name = "Ada"           # str
age = 36               # int
height = 1.72          # float
is_active = True       # bool
tags = ["python", "api"]
profile = {"role": "dev", "remote": True}

Functions

def greet(name: str, loud: bool = False) -> str:
    message = f"Hello, {name}"
    return message.upper() if loud else message


def add(*numbers: int) -> int:
    return sum(numbers)

List and Dict Comprehensions

numbers = [1, 2, 3, 4, 5]
evens_squared = [n**2 for n in numbers if n % 2 == 0]

users = [{"name": "Ada"}, {"name": "Linus"}]
indexed_names = {index: user["name"] for index, user in enumerate(users, start=1)}

Classes

class User:
    def __init__(self, name: str, email: str) -> None:
        self.name = name
        self.email = email

    def greet(self) -> str:
        return f"Hi, I'm {self.name}"

Error Handling (try/except)

def parse_port(value: str) -> int:
    try:
        port = int(value)
        if not (1 <= port <= 65535):
            raise ValueError("Port out of range")
        return port
    except ValueError as error:
        raise ValueError("Invalid port") from error

Common Built-in Functions

names = ["ada", "linus", "grace"]

count = len(names)
sorted_names = sorted(names)
any_short = any(len(name) < 4 for name in names)
all_lowercase = all(name.islower() for name in names)

Virtual Environments Basics

python -m venv .venv
source .venv/bin/activate      # macOS/Linux
.venv\Scripts\activate         # Windows PowerShell
python -m pip install requests
python -m pip freeze > requirements.txt

References

• Python Documentation
• Python Tutorial
• venv — Creation of virtual environments