Environment variables usage in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an environment variable?

An environment variable is a named value stored outside a program that can affect how the program runs. It is like a setting or secret stored in the computer's system that programs can read.

beginner

How do you access environment variables in Python?

You use the os module and call os.getenv('VARIABLE_NAME') to get the value of an environment variable.

intermediate

Why should sensitive information like passwords be stored in environment variables?

Storing sensitive info in environment variables keeps secrets out of the code. This helps keep passwords safe and makes it easier to change them without changing the program.

beginner

What happens if you try to get an environment variable that does not exist using os.getenv?

If the environment variable does not exist, os.getenv returns None by default, or a default value if you provide one.

beginner

How can you set an environment variable in a Unix-like terminal before running a Python script?

You can set it by typing export VARIABLE_NAME=value in the terminal. Then when you run the Python script, it can read that variable.

Which Python module is commonly used to access environment variables?

A os

B sys

C math

D random

The os module provides functions like os.getenv to access environment variables.

What does os.getenv('API_KEY') return if 'API_KEY' is not set?

A An error is raised

B None

C Zero

D An empty string

If the environment variable is not set, os.getenv returns None by default.

Why is it better to store passwords in environment variables rather than hardcoding them?

A It allows passwords to be printed easily

B It makes the program run faster

C It uses less memory

D It keeps passwords secret and separate from code

Storing passwords in environment variables keeps them secret and makes it easier to change them without editing code.

How do you set an environment variable named 'TOKEN' to 'abc123' in a Unix terminal?

A export TOKEN=abc123

B TOKEN=abc123

C set TOKEN=abc123

D env TOKEN abc123

The correct command is export TOKEN=abc123 to set an environment variable in Unix shells.

Which of these is a safe way to provide a default value when reading an environment variable in Python?

A os.getenv('VAR', 'default')

B os.getenv('VAR') or 'default'

C Both B and C

D None of the above

Both os.getenv('VAR', 'default') and os.getenv('VAR') or 'default' safely provide a default value.

Explain how to read an environment variable in Python and why it is useful.

Think about how programs get settings from outside.

Describe how to set an environment variable in a terminal and how a Python script can use it.

Consider the steps before running the Python script.