Software Coding - Python | Explore How-to

Introduction

Latest Python version 3.7.4. Ubuntu 18.04 comes with pre-installed Python 3.6.5.

NOTE: upgrading Python on Ubuntu requires build from source.

References:

Real Python
Excellent Python tutorial website;

Python “modules” and “packages”

Python provides two constructs to facilitate modular programming: modules and packages.

module is the most basic method; module can be built-in, or written in Python, or C. A “python” file (i.e., contains python codes and has py filename extension is a module
package is a grouping of modules in a folder such that it can be referenced using dot notation to avoid module names collision.

Python package is distributed in the form of archived file (.whl). The wheel file is uploaded to repository, Python Package Index and other indexes, to share with others.

pip is the recommended “package installer” for python.

Install `pip`

apt install python3-pip

Use pip to install packages from the Python Package Index and other indexes. Additional setup is needed to pull from other indexes (i.e., package repository) as discussed below.

[ALTERNATIVE] - Download and Install

# Download and install pip
wget https://bootstrap.pypa.io/get-pip.py
sudo python get-pip.py

Setup additional package repository

The setup file is pip.conf, or pip.ini for Windows; that can be found in one or more locations due to: platform variations, or scope (i.e., site-wide, per-user, etc.)

For Ubuntu, the file does not exist by default; can be added to /etc/pip.conf:

[global]
timeout = 60
index-url = https://download.zope.org/ppix

For Raspbian, the default setup, /etc/pip.conf, points to an extra repo:

[global]
extra-index-url=https://www.piwheels.org/simple

For detailed, refer to Pip User Guide

Setup trusted-host

For example,

pip install --trusted-host pypi.python.org

Useful commands

pip install [package-name]
pip uninstall [package-name]
pip search [package-name]
pip freeze > requirements.txt
pip install -r requirements.txt --trusted-host

References

Setup `virtualenv` & `virtualenvwrapper`

It’s a good practice to use isolated virtual environments for prototyping, or starting a completely new Python project especially if introducing new or unfamiliar packages. virtualenv is a tool to create isolated Python environments.

virtualenvwrapper is a set of extensions to virtualenv that include: wrappers for creating and deleting virtual environments, managing development workflow, making it easier to work on more than one project at a time without introducing conflicts in their dependencies.

Installation

Install packages

sudo pip3 install virtualenv virtualenvwrapper
virtualenv --version

Set locations in .bashrc file; the folders for each virtual environment will be stored in the .virtualenvs folder in the user’s $HOME directory;

export WORKON_HOME=$HOME/.virtualenvs
export VIRTUALENVWRAPPER_PYTHON=/usr/bin/python3
source /usr/local/bin/virtualenvwrapper.sh

Reload startup file
```
source ~/.bashrc
```

Create virtual environment

For example, create a new environment called tfserving for a project:

mkvirtualenv tfserving -p python3
workon tfserving

If the project has a preset package requirements specified in the requirements.txt file, then proceed to install. For example,

cd <home_directory>/tfserving_project
pip3 install -r requirements.txt

Exit from the virtual environment

deactivate

Delete virtual environment

rmvirtualenv <ve_name>

Reference

Jupyter

Notebook:

jupyter notebook

JupterLab:

jupyter lab

JupyterHub

JupyterHub Github

Online IDE

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Software Coding - Python