Contents

• Lesson Goals
• Introducing Modules
• Mac and Linux instructions
• Windows Instructions
• Installing Python Modules

Lesson Goals

This lesson shows you how to download and install Python modules. There are many ways to install external modules, but for the purposes of this lesson, we’re going to use a program called pip, easily installable on mac/linux and windows. As of Python 2.7.9 and newer, pip is installed by default. This tutorial will be helpful for anyone using older versions of Python (which are still quite common).

Introducing Modules

One of the great things about using Python is the number of fantastic code libraries that are widely and easily available that can save you a lot of coding, or simply make a particular task (like creating a CSV file, or scraping a webpage) much easier. When Googling for solutions to problems, you’ll often find sample code that uses code libraries you haven’t heard about before. Don’t let these scare you away! Once these libraries are installed on your computer, you can use them by importing them at the beginning of your code; you can import as many libraries as you’d like, such as

import csv
import requests
import kmlwriter
import pprint

For new Python users, it can be a bit intimidating to download and install external modules for the first time. There are many ways of doing it (thus adding to the confusion); this lesson introduces one of the easiest and most common ways of installing python modules.

The goal here is to install software on your computer that can automatically download and install Python modules for us. We’re going to use a program called pip.

Note: As of Python 3.4, pip will be included in the regular install. There are many reasons why you might not have this version yet, and in case you don’t, these instructions should help.

Mac and Linux instructions

As per the pip documentation, we can download a python script to install pip for us. Using a Mac or Linux, we can install pip via the command line by using the curl command, which downloads the pip installation perl script.

curl -O https://bootstrap.pypa.io/get-pip.py

once you’ve downloaded the get-pip.py file, you need to execute it with the python interpreter. However, if you try to execute the script with python like

python get-pip.py

the script will most likely fail because it won’t have permissions to update certain directories on your filesystem that are by default set so that random scripts cannot change important files and give you viruses. In this case—and in all cases where you need to allow a script that you trust to write to your system folders—you can use the sudo command (short for “Super User DO”) in front of the python command, like

sudo python get-pip.py

Windows Instructions

As with the above platforms, the easiest way to install pip is through the use of a python program called get-pip.py, which you can download here. When you open this link, you might be scared of the massive jumble of code that awaits you. Please don’t be. Simply use your browser to save this page under its default name, which is get-pip.py. It might be a good idea to save this file in your python directory, so you know where to find it.

Once you have saved this file, you need to run it, which can be done in two ways. If you prefer using your python interpreter, just right-click on the file get-pip.py and choose “open with” and then choose whatever python interpreter you care to use.

If you prefer to install pip using the windows command line, navigate to whatever directory you’ve placed python and get-pip.py. For this example, we’ll assume this directory is python27, so we’ll use the command C:\>cd python27. Once you are in this directory, to install pip run the command

python get-pip.py

If you want more information or help with a weird error message, check out the StackOverflow page that seems to be regularly updated.

Installing Python Modules

Now that you have pip, it is easy to install python modules since it does all the work for you. When you find a module that you want to use, usually the documentation or installation instructions will include the necessary pip command, such as

pip install requests
pip install beautifulsoup4
pip install simplekml

Remember, for the same reasons explained above (on Mac or Linux systems, but not Windows), you might need to run pip with sudo, like

sudo pip install requests

Sometimes, especially on Windows, you may find it helpful to use the -m flag (to help python find the pip module), like

python -m pip install XXX

Happy installing!