Modules, pip and virtual environments

import loads code from a module. Python ships with many useful ones, like csv, json, datetime and os. Everything else you install with pip.

python

from datetime import date

import os

print(date.today())          # e.g. 2026-10-04

print(os.getenv("DB_HOST"))  # read config from the environment

One environment per project

bash

python -m venv .venv            # create an isolated environment

source .venv/bin/activate       # Windows: .venv\Scripts\activate

pip install pandas              # install into it

pip freeze > requirements.txt   # record exact versions

on the job Keeping each project in its own virtual environment stops package versions from clashing. requirements.txt lets a teammate, or a server, rebuild exactly the same setup.