Python install environment variables

How to Set and Get Environment Variables in Python

To set and get environment variables in Python you can just use the os module:

import os # Set environment variables os.environ['API_USER'] = 'username' os.environ['API_PASSWORD'] = 'secret' # Get environment variables USER = os.getenv('API_USER') PASSWORD = os.environ.get('API_PASSWORD') # Getting non-existent keys FOO = os.getenv('FOO') # None BAR = os.environ.get('BAR') # None BAZ = os.environ['BAZ'] # KeyError: key does not exist. 

Note that using getenv() or the get() method on a dictionary key will return None if the key does not exist. However, in the example with BAZ , if you reference a key in a dictionary that does not exist it will raise a KeyError .

Environment variables are useful when you want to avoid hard-coding access credentials or other variables into code. For example, you may need to pass in API credentials for an email service provider in order to send email notifications but you wouldn’t want these credentials stored in your code repository. Or perhaps you need your code to function slightly differently between your development, staging and production environments. In this case you could pass in an environment variable to tell your application what environment it’s running in. These are typical use cases for environment variables.

Storing local env variables

You should write your Python code so that it is able to access environment variables from whatever environment it is running in. This could be either your local virtual environment that you’re using for development or a service that you are hosting it on. A useful package that simplifies this process is Python Decouple, this is how you would use it.

First install Python Decouple into your local Python environment.

$ pip install python-decouple 

Once installed, create a .env file in the root of your project which you can then open up to add your environment variables.

$ touch .env # create a new .env file $ nano .env # open the .env file in the nano text editor 

‌You can then add your environment variables like this:

USER=alex KEY=hfy92kadHgkk29fahjsu3j922v9sjwaucahf 

Then save (WriteOut) the file and exit nano. Your environment variables are now stored in your .env file. If you’re using git, remember to add .env to your .gitignore file so that you don’t commit this file of secrets to your code repository.

Now that you have your environment variables stored in a .env file, you can access them in your Python code like this:

from decouple import config API_USERNAME = config('USER') API_KEY = config('KEY') 

The benefit of using something like the above approach is that when you deploy your application to a cloud service, you can set your environment variables using whatever method or interface the provider has and your Python code should still be able to access them. Note that it is common convention to use capital letters for names of global constants in your code.

Most cloud service providers will have a CLI or web interface that lets you configure the environment variables for your staging or production environments. For guidance in these cases you ‘ll need to refer to their documentation on how to set environment variables when using their service.

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Python — Environment Setup

Python is available on a wide variety of platforms including Linux and Mac OS X. Let’s understand how to set up our Python environment.

• Unix (Solaris, Linux, FreeBSD, AIX, HP/UX, SunOS, IRIX, etc.)
• Win 9x/NT/2000
• Macintosh (Intel, PPC, 68K)
• OS/2
• DOS (multiple versions)
• PalmOS
• Nokia mobile phones
• Windows CE
• Acorn/RISC OS
• BeOS
• Amiga
• VMS/OpenVMS
• QNX
• VxWorks
• Psion

Python has also been ported to the Java and .NET virtual machines

Local Environment Setup

Open a terminal window and type «python» to find out if it is already installed and which version is installed. If Python is already installed then you will get a message something like as follows:

$ python Python 3.6.8 (default, Sep 10 2021, 09:13:53) [GCC 8.5.0 20210514 (Red Hat 8.5.0-3)] on linux Type "help", "copyright", "credits" or "license" for more information. >>>

Getting Python

The most up-to-date and current source code, binaries, documentation, news, etc., is available on the official website of Python https://www.python.org/

You can download Python documentation from https://www.python.org/doc/. The documentation is available in HTML, PDF, and PostScript formats.

Installing Python

Python distribution is available for a wide variety of platforms. You need to download only the binary code applicable for your platform and install Python.

If the binary code for your platform is not available, you need a C compiler to compile the source code manually. Compiling the source code offers more flexibility in terms of choice of features that you require in your installation.

Here is a quick overview of installing Python on various platforms −

Unix and Linux Installation

Here are the simple steps to install Python on Unix/Linux machine.

• Open a Web browser and go to https://www.python.org/downloads/.
• Follow the link to download zipped source code available for Unix/Linux.
• Download and extract files.
• Editing the Modules/Setup file if you want to customize some options.

Now issue the following commands:

$ run ./configure script $ make $ make install

This installs Python at standard location /usr/local/bin and its libraries at /usr/local/lib/pythonXX where XX is the version of Python.

Using Yum Command

Red Hat Enterprise Linux (RHEL 8) does not install Python 3 by default. We usually use yum command on CentOS and other related variants. The procedure for installing Python-3 on RHEL 8 is as follows:

Windows Installation

Here are the steps to install Python on Windows machine.

• Open a Web browser and go to https://www.python.org/downloads/.
• Follow the link for the Windows installer python-XYZ.msi file where XYZ is the version you need to install.
• To use this installer python-XYZ.msi, the Windows system must support Microsoft Installer 2.0. Save the installer file to your local machine and then run it to find out if your machine supports MSI.
• Run the downloaded file. This brings up the Python install wizard, which is really easy to use. Just accept the default settings, wait until the install is finished, and you are done.

Macintosh Installation

Recent Macs come with Python installed, but it may be several years out of date. See http://www.python.org/download/mac/ for instructions on getting the current version along with extra tools to support development on the Mac. For older Mac OS’s before Mac OS X 10.3 (released in 2003), MacPython is available.

Jack Jansen maintains it and you can have full access to the entire documentation at his website − http://www.cwi.nl/~jack/macpython.html. You can find complete installation details for Mac OS installation.

Setting up PATH

Programs and other executable files can be in many directories, so operating systems provide a search path that lists the directories that the OS searches for executables.

The path is stored in an environment variable, which is a named string maintained by the operating system. This variable contains information available to the command shell and other programs.

The path variable is named as PATH in Unix or Path in Windows (Unix is case sensitive; Windows is not).

In Mac OS, the installer handles the path details. To invoke the Python interpreter from any particular directory, you must add the Python directory to your path.

Setting path at Unix/Linux

To add the Python directory to the path for a particular session in Unix −

• In the csh shell − type setenv PATH «$PATH:/usr/local/bin/python» and press Enter.
• In the bash shell (Linux) − type export PATH=»$PATH:/usr/local/bin/python» and press Enter.
• In the sh or ksh shell − type PATH=»$PATH:/usr/local/bin/python» and press Enter.
• Note − /usr/local/bin/python is the path of the Python directory

Setting path at Windows

To add the Python directory to the path for a particular session in Windows −

At the command prompt − type path %path%;C:\Python and press Enter.

Note − C:\Python is the path of the Python directory

Python Environment Variables

Here are important environment variables, which can be recognized by Python −

It has a role similar to PATH. This variable tells the Python interpreter where to locate the module files imported into a program. It should include the Python source library directory and the directories containing Python source code. PYTHONPATH is sometimes preset by the Python installer.

It contains the path of an initialization file containing Python source code. It is executed every time you start the interpreter. It is named as .pythonrc.py in Unix and it contains commands that load utilities or modify PYTHONPATH.

It is used in Windows to instruct Python to find the first case-insensitive match in an import statement. Set this variable to any value to activate it.

It is an alternative module search path. It is usually embedded in the PYTHONSTARTUP or PYTHONPATH directories to make switching module libraries easy.

Running Python

There are three different ways to start Python −

Interactive Interpreter

You can start Python from Unix, DOS, or any other system that provides you a command-line interpreter or shell window.

Enter python the command line.

Start coding right away in the interactive interpreter.

$python # Unix/Linux or python% # Unix/Linux or C:> python # Windows/DOS

Here is the list of all the available command line options −

It generates optimized bytecode (resulting in .pyo files).

Do not run import site to look for Python paths on startup.

verbose output (detailed trace on import statements).

disable class-based built-in exceptions (just use strings); obsolete starting with version 1.6.

run Python script sent in as cmd string

run Python script from given file

Script from the Command-line

A Python script can be executed at command line by invoking the interpreter on your application, as in the following −

$python script.py # Unix/Linux or python% script.py # Unix/Linux or C: >python script.py # Windows/DOS

Note − Be sure the file permission mode allows execution.

Integrated Development Environment

You can run Python from a Graphical User Interface (GUI) environment as well, if you have a GUI application on your system that supports Python.

• Unix − IDLE is the very first Unix IDE for Python.
• Windows − PythonWin is the first Windows interface for Python and is an IDE with a GUI.
• Macintosh − The Macintosh version of Python along with the IDLE IDE is available from the main website, downloadable as either MacBinary or BinHex’d files.

If you are not able to set up the environment properly, then you can take help from your system admin. Make sure the Python environment is properly set up and working perfectly fine.

We have provided Python Online Compiler/Interpreter which helps you to Edit and Execute the code directly from your browser. Try to click the icon to run the following Python code to print conventional «Hello, World!».

Below code box allows you to change the value of the code. Try to change the value inside print() and run it again to verify the result.

# This is my first Python program. # This will print 'Hello, World!' as the output print ("Hello, World!");

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