Reference library

Functions & basics

Reusable building blocks — parameters, returns, scope, and clear function design.

4 matches

Build a Context Manager in Python with contextlib.contextmanager

Create a reusable context manager that safely opens and closes files using the contextlib contextmanager decorator.

context manager contextlib file handling

from contextlib import contextmanager

@contextmanager
def managed_file(filename, mode='r'):
    """Context manager that opens and closes a file safely."""
    file = open(filename, mode)
    yield file
    file.close()

if __name__ == "__main__":
    # Write a sample file
    with managed_file("sample.txt", "w") as f…

15 0 Open

Functions & basics easy

How to Load a .env File Manually in Python

Parse a .env-style key-value file into a Python dictionary using only the standard library, with comment and quoted-value handling.

dotenv environment-variables file-parsing

Python

import re
from pathlib import Path


def load_dotenv_file(filepath: str) -> dict[str, str]:
    """Parse a .env-style file into a dictionary."""
    env = {}
    path = Path(filepath)

    if not path.exists():
        raise FileNotFoundError(f"Environment file not found: {filepath}")

    for line in path.read_text()…

13 0 Open

Functions & basics easy

How to Write a Context Manager Class in Python

Define a class with __enter__ and __exit__ to manage file resources safely using the with statement.

context-manager with-statement resource-management

Python

class FileReader:
    def __init__(self, filename, mode="r"):
        self.filename = filename
        self.mode = mode
        self.file = None

    def __enter__(self):
        self.file = open(self.filename, self.mode)
        return self.file

    def __exit__(self, exc_type, exc_val, exc_tb):
        if self.file…

13 0 Open

Functions & basics easy

Profile Python functions with cProfile

Profile a Python program with cProfile, capture the stats in memory, and print a sorted performance report.

cprofile performance profiling

Python

import cProfile
import pstats
import io


def slow_function():
    total = 0
    for i in range(100000):
        total += i ** 2
    return total


def medium_function():
    return sum(range(10000))


def fast_function():
    return sum(range(100))


def main():
    result1 = slow_function()
    result2 = medium_func…

11 0 Open

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