Python has a strong community which releases lot's of modules(packages), which you can use for free and focus on "get job done", instead of reinventing the wheel.

pip is the tool for installing Python packages from PyPI (Python Package Index)

Note, that by using pip, a package will be installed in your system's python distribution.

pip basic commands

get help on pip:

pip help

list installed packages:

pip list

install a package from PyPI:

pip install package_name

uninstall a package

pip uninstall package_name

list outdated packages:

pip list --outdated

upgrade a package:

pip install --upgrade SomePackage

More readings

pip - The PyPA recommended tool for installing Python packages.

PyPI - the Python Package Index

Virtual environment - Why?

Python apps usually depends on many modules(packages), which depends on other packages, and very often - from a specific version of a package.

Many system tools also depends on specific versions of installed Python packages.

You don't want to pollute your system's Python environment!

Virtual environment - What?

Virtual environments create an isolated Python environment for your project.

Keep workflows between projects independent.

Keeps dependency hell away.

There are many tools for working with virtual environments in Python (virtualenv, pyenv, venv, virtualenvwrapper)

and pipenv

Pipenv - What?

A dependency and virtual environments manager combined into one.

Automatically creates and manages a virtualenv for your projects.

The officially recommended Python packaging tool

Functionally similar to npm and other modern package managers.

docs.pipenv.org

pipenv Documentation - Release 2018.05.18

Pipenv - Install

			$ pip install --user pipenv
		

Pipenv - set up PATH

If pipenv isn’t available in your shell after installation, you'll need to add the user base's binary directory to your PATH.

find the user base binary directory, and:

Linux and macOS:

					python -m site --user-base
					# /home/username/.local

					# add it to your ~/.profile or ~/.bashrc file, or:
					export PATH=$PATH:/home/username/.local/bin
			

Windows:

				py -m site --user-site
				#C:\Users\Username\AppData\Roaming\Python36\site-packages

				# add to PATH:
				C:\Users\Username\AppData\Roaming\Python36\Scripts
			

You may need to log out for the PATH changes to take effect.

Pipenv - manage virtualenv

				### Create virtualenv with system Python3:
				$ pipenv --three
				Creating a virtualenv for this project…


				### Spawn a shell within the virtualenv
				$ pipenv shell
				Spawning environment shell...

				### Exit the virtualenv
				(course_intro-SmgljMaj) $ exit
				exit
				$

				### Output virtualenv information
				$ pipenv --venv

				### Remove the virtualenv
				$ pipenv --rm
				Removing virtualenv...
		

All options available with: pipenv --help

PIPENV_VENV_IN_PROJECT

Pipenv creates virtualenv automatically for you and stores it in a predefined path and gives it a random prefixed name.

There is no way to control the name of the virtual environment being created.

But if you set the environment variable PIPENV_VENV_IN_PROJECT=1, pipenv will store the virtualenv in .venv/ folder per project bases and will name the virtualenv after your project name.

Pipenv - manage packages for your project

			### install requests package and create a virenv, if there is no one
			$ pipenv install requests
			Installing requests…

			### remove package
			$ pipenv uninstall requests
			Uninstalling requests-2.18.4
		

List as a graph the installed packages for the given virtualenv

			$ pipenv graph
		

Use the installed module in your program

Create a file my_ip.py

Write in it:

				import requests

				response = requests.get('https://httpbin.org/ip')

				print('Your IP is {0}'.format(response.json()['origin']))
			

Execute your program within the pipenv shell:

				(course_intro-SmgljMaj) $ python my_ip.py
			

Exit the virtual environment

			exit
		

Or type ctrl-d

Or close your terminal window :)

Useful video

Intro to Pipenv - A Package Manager for Python by Pretty Printed

Useful video

Install Python, PIP, Virtualenv, and Django on Windows 10 with PowerShell by CodingEntrepreneurs

Pipenv - note

We'll speak more on importing modules and managing dependencies in the theme "Organizing code: more on importing modules", but for now remeber just to use pipenv instead of pip whenever you want to play with some Python module/code.

Create the file

create the file "simple_plot.py" in your project root folder.

Enter in it the code bellow:

			import matplotlib.pyplot as plt
			import numpy as np

			t = np.arange(0.0, 2.0, 0.01)
			s = 1 + np.sin(2*np.pi*t)
			plt.plot(t, s)

			plt.xlabel('time (s)')
			plt.ylabel('voltage (mV)')
			plt.title('About as simple as it gets, folks')
			plt.grid(True)
			plt.savefig("test.png")
			plt.show()
		

example from: matplotlib.org

Prepare terminal

Open a terminal window and navigate to your project root folder.

Make sure you are in it:

			# navigate...
			$ cd your/project/root/folder

			# make sure you are in it - get your current working directory:
			$ pwd
			your/project/root/folder
		

Run the program

try to run the simple_plot.py program

			$ python simple_plot.py
			Traceback (most recent call last):
			  File "simple_plot.py", line 1, in <module>
			    import matplotlib.pyplot as plt
			ImportError: No module named matplotlib.pyplot
		

Yes, an error occurs, because we do not have the required module (matplotlib) installed

Install dependencies in a virtual environment

We will install the required modules in a safe virtual environment by pipenv!

			# install packages safely with pipenv:
			$ pipenv install matplotlib
			Creating a virtualenv for this project…
			...
			To activate this project`s virtualenv, run the following
			  $ pipenv shell
		

Activate the virtual environment

				$ pipenv shel
				  Spawning environment shell...
			

Run the program within the virtual environment

Run the simple_plot.py program:

				python simple_plot.py
			

It should run now - a windows with simple plots wil be opened:

All the steps in a gif

Get the virtual environment's python path:

				# navigate to project folder
				$ cd your/root/project/folder

				# get into pipenv shell
				$ pipenv shell
				(my_project-hUoR8K1v) $

				# get python path and copy it
				(my_project-hUoR8K1v) $ which python
					/home/nemsys/.local/share/virtualenvs/my_project-hUoR8K1v/bin/python
			

Set the virtual environment's python path for vs code

Open VS Code project workspace settings.

ctrl+shift+p and find Preferences: Open Workspace Settings

search for python.pythonPath in left panel

click "edit" icon and "copy to settings"

in the right panel paste the pipenv venv path into the "python.pythonPath" value

Workspace settings after the change

Your workspace settings should look like:

				{
					"folders": [
						{
							"path": "."
						}
					],
					"settings": {
						"python.pythonPath": "/home/nemsys/.local/share/virtualenvs/my_project-hUoR8K1v/bin/python"
					}
				}
			

Run the program

Right click on the editor area and select "Run Python File in Terminal "

pipenv with VS Code - as gif

Exercises

simple_plot with matplotlib

Look again at the "Example: simple_plot with matplotlib" and repeat the steps on your machine, such that the program "simple_plot.py" will run without errors