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Setting Environment Variables

Setting Environment Variables in Python

Introduction

Environment variables are system-level settings that store configuration values used by applications and operating systems. They allow programs to access important information such as file paths, API keys, database credentials, and system configurations without hardcoding them into the source code.

When working with Python, setting environment variables is an important step because it helps Python locate executables, libraries, and configuration settings. Environment variables are widely used in software development, automation testing, DevOps, and cloud applications.

In this tutorial, you will learn what environment variables are, why they are important, and how to configure them on Windows, macOS, and Linux systems.

What Are Environment Variables?

Environment variables are dynamic values stored by the operating system that can be accessed by applications and scripts during execution.

Examples of common environment variables include:

  • PATH

  • HOME

  • USERNAME

  • TEMP

  • JAVA_HOME

  • PYTHONPATH

These variables help applications determine where files, programs, and configurations are located.

Why Are Environment Variables Important?

Environment variables provide several benefits:

  • Avoid hardcoding sensitive information

  • Simplify application configuration

  • Improve portability across environments

  • Enable centralized configuration management

  • Allow programs to locate required files and executables

In Python development and automation testing, environment variables are frequently used to store:

  • API keys

  • Database credentials

  • Application URLs

  • Browser paths

  • Test environment settings

Understanding the PATH Variable

The PATH variable is one of the most important environment variables.

It contains a list of directories that the operating system searches when a command is executed.

For example, when you run:

python

the operating system looks through the directories listed in PATH to locate the Python executable.

Without Python being added to PATH, you may receive an error such as:

'python' is not recognized as an internal or external command

What is PYTHONPATH?

PYTHONPATH is an environment variable used by Python to locate additional modules and packages.

When Python starts, it searches for modules in:

  • Current directory

  • Standard library directories

  • Directories specified in PYTHONPATH

This is useful when working with custom modules stored outside the default locations.

Viewing Environment Variables in Windows

To view environment variables in Windows:

Method 1

  1. Open the Start Menu.

  2. Search for “Environment Variables”.

  3. Click Edit the system environment variables.

  4. Click Environment Variables.

You will see:

User Variables

Variables available only to the current user.

System Variables

Variables available to all users on the system.

Viewing Environment Variables Using Command Prompt

Open Command Prompt and run:

set

This displays all currently configured environment variables.

To view a specific variable:

echo %PATH%

Example:

C:\Python313\;C:\Python313\Scripts\

Setting Environment Variables in Windows

Method 1: Using the Environment Variables Window

Step 1

Open:

Environment Variables

Step 2

Select either:

  • User Variables

  • System Variables

Step 3

Click:

New

Step 4

Enter:

Variable Name:

MY_VARIABLE

Variable Value:

HelloPython

Step 5

Click:

OK

The variable is now saved.

Verifying the Variable

Open a new Command Prompt window and run:

echo %MY_VARIABLE%

Output:

HelloPython

Adding Python to PATH Manually

Sometimes Python is installed but not added to PATH.

To add Python manually:

Step 1

Locate the Python installation directory.

Example:

C:\Python313\

Step 2

Open Environment Variables.

Step 3

Select:

Path

Step 4

Click:

Edit

Step 5

Add:

C:\Python313\

and

C:\Python313\Scripts\

Step 6

Save the changes.

Step 7

Open Command Prompt and verify:

python --version

Example Output:

Python 3.13.0

Setting Temporary Environment Variables in Windows

You can create variables that exist only for the current Command Prompt session.

Example:

set PROJECT_NAME=PythonTutorial

Verify:

echo %PROJECT_NAME%

Output:

PythonTutorial

Once the Command Prompt window closes, the variable is removed.

Setting Environment Variables in PowerShell

Create a variable:

$env:PROJECT_NAME="PythonTutorial"

Display the value:

$env:PROJECT_NAME

Output:

PythonTutorial

Setting Environment Variables in Linux

Open Terminal and create a temporary variable:

export PROJECT_NAME=PythonTutorial

Verify:

echo $PROJECT_NAME

Output:

PythonTutorial

Creating Permanent Variables in Linux

Open:

~/.bashrc

or

~/.profile

Add:

export PROJECT_NAME=PythonTutorial

Save the file and reload:

source ~/.bashrc

Verify:

echo $PROJECT_NAME

Setting Environment Variables in macOS

Open Terminal and edit:

~/.zshrc

Add:

export PROJECT_NAME=PythonTutorial

Save the file and reload:

source ~/.zshrc

Verify:

echo $PROJECT_NAME

Output:

PythonTutorial

Accessing Environment Variables in Python

Python provides the os module to access environment variables.

Example:

import os

value = os.getenv("PROJECT_NAME")

print(value)

Output:

PythonTutorial

Reading the PATH Variable in Python

Example:

import os

print(os.getenv("PATH"))

This displays all directories stored in the PATH environment variable.

Setting Environment Variables in Python

You can create environment variables during program execution.

Example:

import os

os.environ["PROJECT_NAME"] = "PythonTutorial"

print(os.environ["PROJECT_NAME"])

Output:

PythonTutorial

Note that this variable exists only while the program is running.

Environment Variables in Automation Testing

Environment variables are heavily used in automation testing.

Common examples include:

Application URL

TEST_URL=https://test.example.com

Username

USERNAME=testuser

Password

PASSWORD=SecurePassword

API Key

API_KEY=123456789

Automation frameworks can read these values dynamically instead of hardcoding them.

Advantages of Using Environment Variables

Security

Sensitive information is not stored directly in source code.

Flexibility

Configurations can change without modifying code.

Reusability

The same script can run in multiple environments.

Maintainability

Centralized configuration simplifies updates.

Best Practices

When working with environment variables:

  • Use meaningful variable names.

  • Avoid hardcoding passwords.

  • Store sensitive data securely.

  • Document required variables.

  • Separate development and production configurations.

  • Use environment-specific settings.

Common Mistakes

Forgetting to Restart Terminal

Some changes require reopening the terminal or command prompt.

Typing Errors

Incorrect variable names can cause configuration issues.

Missing PATH Configuration

Python commands may not work if PATH is not configured correctly.

Exposing Sensitive Information

Never store passwords or API keys directly in source code repositories.

Real-World Example

Suppose you have an automation framework that runs against different environments.

Instead of writing:

url = "https://test.example.com"

You can use:

import os

url = os.getenv("TEST_URL")

This allows the same script to run in:

  • Development

  • Testing

  • Staging

  • Production

without changing the code.

Conclusion

Environment variables play a critical role in Python development and automation testing. They help applications store configuration values securely and make software easier to maintain and deploy across different environments.

Understanding how to create, modify, and access environment variables is an essential skill for Python developers, automation engineers, and DevOps professionals. By using environment variables effectively, you can build more secure, flexible, and scalable applications.

Frequently Asked Questions (FAQs)

What are environment variables?

Environment variables are system-level settings that store configuration values used by applications and operating systems.

Why is PATH important?

The PATH variable helps the operating system locate executable programs such as Python.

What is PYTHONPATH?

PYTHONPATH is an environment variable that tells Python where to look for additional modules and packages.

Can Python read environment variables?

Yes. Python can read environment variables using the os.getenv() function.

Why are environment variables used in automation testing?

They help store configuration values such as URLs, usernames, passwords, and API keys without hardcoding them into scripts.

Key Takeaways

  • Environment variables store configuration information used by applications.

  • PATH is the most important variable for locating Python executables.

  • PYTHONPATH helps Python find custom modules and packages.

  • Environment variables can be created temporarily or permanently.

  • Python accesses environment variables using the os module.

  • Automation frameworks commonly use environment variables for configuration management.

  • Using environment variables improves security, flexibility, and maintainability.