The missing guide for setting up a great local development workflow for your Python projects.
---------------------------------------------------------------------------------------------

This is an **opinionated** way of developing with Python locally. You’ve probably discovered that it’s a pain in the ass to manage different projects with dependencies targeting different Python versions on your local machine.

To complicate things, there are multiple ways of installing Python too:

*   Preinstallation by the OS 😔
*   Using a package manager like `brew` or `apt` 😕
*   Using the binaries from [www.python.org](http://www.python.org/) 😫
*   Using [pyenv](https://github.com/pyenv/pyenv)—easy way to install and manage Python installations 😎

> **_This guide uses_** [**_pyenv_**](https://github.com/pyenv/pyenv) **_to manage Python installations, and_** [**_Pipenv_**](https://github.com/pypa/pipenv) **_to manage project dependencies (instead of raw pip)._**

### Installing pyenv

Let’s install via `brew`:

**$ brew install pyenv**

_If you’re not on Mac, please see pyenv’s_ [_installation instructions_](https://github.com/pyenv/pyenv#installation)_._

Add the following to your `~/.bash_profile` , or `~/.bashrc` (depending on your shell) to automatically initialize pyenv when your terminal loads:

**eval "$(pyenv init -)"**

### How does pyenv work?

See all available Python versions:

    $ pyenv install --list

Let’s install Python 3.6.6

**$ pyenv install 3.6.6**

Installed Python-3.6.6 to /Users/dvf/.pyenv/versions/3.6.6

pyenv won’t change your global interpreter unless you tell it to:

**$ python --version**

Python 2.7.14

**$ pyenv global 3.6.6**

Python 3.6.6

pyenv allows you to install different versions of Python **local** to a directory. Let’s create a project targeting Python 3.7.0:

**$ pyenv install 3.7.0**

Installed Python-3.7.0 to /Users/dvf/.pyenv/versions/3.7.0

**$ mkdir my\_project && cd my\_project  
$ python --version**

Python 3.6.6

**$ pyenv local 3.7.0  
$ python --version**

Python 3.7.0

Now whenever you find yourself in `my_project` you’ll automatically use the Python 3.7.0 interpreter.

> **_🤚Did that make sense?_** If not, stop here and take some time to play around with pyenv—it works by installing all Python interpreters in `~/.pyenv` and dynamically adjusting your `$PATH` depending on your current directory.

### What is Pipenv and how does it work?

[Pipenv](https://pipenv.readthedocs.io/en/latest/) is the officially recommended way of managing project dependencies. Instead of having a `requirements.txt` file in your project, and managing virtualenvs, you'll now have a `Pipfile` in your project that does all this stuff automatically.

Start off by installing it via `pip`, it’s a rapidly evolving project so make sure you have the latest version (2018.10.13 at the time of writing):

$ pip install -U pipenv

#### Using Pipenv for the first time

Let’s set up Pipenv in your project:

**$ cd my\_project  
$ pipenv install**

Creating a virtualenv for this project…

Pipfile: /Users/dvf/my\_project/Pipfile

Using /Users/dvf/.pyenv/versions/3.7.0/bin/python3.7 (3.7.0) to create virtualenv…

You’ll find two new files in your project: `Pipfile` and `Pipfile.lock`.

> If you’re installing in a pre-existing project, Pipenv will convert your old `requirements.txt` into a `Pipfile`. How cool is that?

This is what your `Pipfile` should look like for a fresh project:

\[\[source\]\]  
url = "https://pypi.org/simple"  
verify\_ssl = true  
name = "pypi"

\[packages\]

\[dev-packages\]

\[requires\]  
python\_version = "3.7"

**Notice that we didn’t activate any virtual environments here**, Pipenv takes care of virtual environments for us. So, installing new dependencies is simple:

**$ pipenv install django**

Installing django  
...

Installing collected packages: pytz, django  
Successfully installed django-2.1.2 pytz-2018.5

Adding django to Pipfile's \[packages\]…  
Pipfile.lock (4f9dd2) out of date, updating to (a65489)…  
Locking \[dev-packages\] dependencies…  
Locking \[packages\] dependencies…  
Updated Pipfile.lock (4f9dd2)!

Installing dependencies from Pipfile.lock (4f9dd2)…

🐍   ▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉ 2/2 — 00:00:01

To activate this project's virtualenv, run pipenv shell.  
Alternatively, run a command inside the virtualenv with pipenv run.

If you inspect your `Pipfile` you’ll notice it now contains `django = "*"` as a dependency.

If we wanted to install dev dependencies for use during development, for example [YAPF](https://github.com/google/yapf), you’d add `--dev` to the install step:

$ pipenv install --dev yapf

#### **What is** `**Pipfile.lock**`**?**

`Pipfile.lock` is super important because it does two things:

1.  Provides good security by keeping a hash of each package installed.
2.  Pins the versions of all dependencies and sub-dependencies, giving you replicable environments.

Let’s see what it currently looks like:

{  
    "\_meta": {  
        "hash": {  
            "sha256": "627ef89...64f9dd2"  
        },  
        "pipfile-spec": 6,  
        "requires": {  
            "python\_version": "3.7"  
        },  
        "sources": \[  
            {  
                "name": "pypi",  
                "url": "[https://pypi.org/simple](https://pypi.org/simple)",  
                "verify\_ssl": true  
            }  
        \]  
    },  
    "default": {  
        "django": {  
            "hashes": \[  
                "sha256:acdcc1...ab5bb3",  
                "sha256:efbcad...d16b45"  
            \],  
            "index": "pypi",  
            "version": "==2.1.2"  
        },  
        "pytz": {  
            "hashes": \[  
                "sha256:a061aa...669053",  
                "sha256:ffb9ef...2bf277"  
            \],  
            "version": "==2018.5"  
        }  
    },  
    "develop": {}  
}

Notice that the versions of each dependency are pinned. Without a _very_ good reason, you would always want this file committed to your source control.

#### Custom Indexes

Until Pipenv it was difficult to use _private_ Python repositories, for example if you’d like to host private Python libraries within your organization. Now all you need to do is define them as an additional sources in the `Pipfile`:

    [[source]]url = "https://pypi.org/simple"verify_ssl = truename = "pypi"[[source]]url = "https://www.example.com"verify_ssl = truename = "some-repo-name"[packages]django = "*"my-private-app = {version="*", index="some-repo-name"}[dev-packages][requires]python_version = "3.7"

Notice that we told `my-private-app` to use the private repo. If omitted, Pipenv will cycle through indexes until it finds the package.

> **_💡Pipenv will also consume any environment variables in values_**_, which is useful if you have sensitive credentials you don’t want sitting in source control (this was my contribution_ `_</humblebrag>_`_)_

#### Deploying

When deploying it’s important that your deploy fails if there’s a mismatch between installed dependencies and the `Pipfile.lock`. So you should append `--deploy` to your install step which does just that:

    $ pipenv install --deploy

You could also check which dependencies are mismatched:

    $ pipenv check

And see which sub-dependencies are installed by packages:

**$ pipenv graph --reverse**

**pip==18.1**  
**pytz==2018.5**  
  - Django==2.1.2 \[requires: pytz\]  
**setuptools==40.4.3**  
**wheel==0.32.2**  
**yapf==0.24.0**

#### Once-off commands, scripts and activating venvs

If you’re actively developing a project, it’s helpful to activate the virtual environment:

    $ pipenv shell

    Launching subshell in virtual environment…

Or, if you’d like to execute a command inside the venv:

    $ pipenv run python manage.py runserver

You can also add scripts to `Pipfile` similar to `npm` `package.json`:

\[\[source\]\]  
url = "[https://pypi.org/simple](https://pypi.org/simple)"  
verify\_ssl = true  
name = "pypi"

\[packages\]  
django = "\*"

\[dev-packages\]  
yapf = "\*"

\[scripts\]  
server = "python manage.py runserver"

\[requires\]  
python\_version = "3.7"

Now you can execute the script:

**$ pipenv run server**

We’ve just touched the tip of the iceberg. If you’ve like to learn more about Pipenv, I encourage you to read the [great documentation](https://pipenv.readthedocs.io).

> I hope this was helpful to you. And I’d love to hear any thoughts or suggestions you have in the comments!

Why you should use pyenv + Pipenv for your Python projects

Too Long; Didn't Read

Companies Mentioned

@vanflymen

RELATED STORIES