I have been using Ruby professionally for more than a decade now. Until recently, I haven’t explored much outside of the Ruby and Rails community. That changed however after I completed a course in Foundations of Data Science. This made me curious about Python and how to build applications using it.

Python and Ruby have many similarities. Both are interpreted, high-level programming languages. Python also has support for Object-Oriented Programming and Functional Programming. In terms of syntax, they have a similar look and feel, aside from some fundamental differences such as Python being indent-driven.

You may find this article to be very similar to the Ruby on Rails guide I posted years ago. This is not accidental since my goal is to introduce Python web application development to someone who is already familiar in the Ruby space.

Installing Python

The very first step is to install Python itself in your computer. I recommend using pyenv to manage your Python versions. pyenv is a Python version manager, like rbenv. In fact, pyenv is a fork of rbenv and is re-purposed for Python. To install pyenv:

curl https://pyenv.run | bash

After installing, update your login shell configuration by adding the following, e.g. in ~/.zshrc

export PATH="/home/user/.pyenv/bin:$PATH" eval "$(pyenv init -)" eval "$(pyenv virtualenv-init -)"

Now we are ready to use pyenv to install a specific Python version. But first, we need to install some dependencies so we can compile Python from source:

sudo apt-get install -y make build-essential libssl-dev zlib1g-dev libbz2-dev \
libreadline-dev libsqlite3-dev wget curl llvm libncurses5-dev libncursesw5-dev \
xz-utils tk-dev libffi-dev liblzma-dev python-openssl

Then, we can easily install a Python version, like 3.6.8 in this example:

pyenv install 3.6.8

If you are having trouble installing Python, it could be related to the OpenSSL version installed in your machine.

On Debian stretch (and Ubuntu bionic), libssl-dev is OpenSSL 1.1.x,
but support for that was only added in Python 2.7.13, 3.5.3 and 3.6.0.
To install earlier versions, you need to replace libssl-dev with
libssl1.0-dev. This is being tracked in
https://github.com/pyenv/pyenv/issues/945.

Once Python has been installed, you can opt to set the version (e.g 3.6.8) as your global version. This makes the Python executable available to all terminal sessions:

pyenv global 3.6.8

Package Management

pip is Python’s package manager, like rubygems or npm. If you installed Python, pip should also be available for you. If for some reason it is not installed, you can install it using the guide here.

curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py $ python get-pip.py

Application-specific Packages

In Ruby/Rails we use the awesome library Bundler to handle application package management. We manage the packages using a Gemfile, and it gets converted into Gemfile.lock.

pipenv is similar to bundler, but its functionality extends beyond package management in the application. In this article we will use it similar to bundler so it will handle all the application package dependencies. To install pipenv, just use pip!

pip install pipenv

To specify the application packages, pipenv uses a Pipfile. An example is given below:

[[source]]
name = "pypi"
url = "https://pypi.org/simple"
verify_ssl = true

[dev-packages]

[packages]
requests = "*"
flask = "*"
python-dotenv = "*"
flask-sqlalchemy = "*"
flask-migrate = "*"

[requires]
python_version = "3.6" read more