---
canonical: "https://www.jsolly.com/blog/Achieve-consistent-builds-with-Python-constraints/"
title: "Streamlining Dependency Management: Using Constraints Files in Django"
description: "Use a constraints.txt file with pip install to ensure sub-dependencies won't break your app: A guide to set up requirements.txt and constraints.txt files."
author: "John Solly"
published: "2022-07-11T00:49:45.283Z"
updated: "2024-12-23T23:19:48.808Z"
---

<a id="streamlining-dependency-management-using-constraints-files-in-django"></a>

# Streamlining Dependency Management: Using Constraints Files in Django

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> Constraints files are requirements files that only control which version of a requirement is installed, not whether it is installed or not.
> 
> \- [Pip documentation](https://pip.pypa.io/en/stable/user_guide/#constraints-files)

In a [previous post](https://www.jsolly.com/blog/why-I-stopped-using-pip-freeze/), I talked about ditching pip freeze because it didn't work well with second-level dependencies (especially cross-platform). I found an even better workflow where I use a requirements.txt and a constraints.txt file together. Check out the code in [this commit](https://github.com/jsolly/awesome-django-blog/commit/b4e10f7f2e8ac7ce69233d26e0ffa593af3ad6f7).

<pre><code class="language-bash">requirements
├── constraints.txt
└── requirements.txt</code></pre>

Just add a second flag to pip install.

<pre><code class="language-python">python3 -m pip install -r requirements.txt -c constraints.txt</code></pre>

Inside [requirements.txt](https://github.com/jsolly/awesome-django-blog/blob/master/requirements.txt) are packages blogthedata directly uses. 

<pre><code class="language-bash"># requirements.txt
black
Brotli
chromedriver-autoinstaller
coverage
Django
...</code></pre>

Constraints.txt  includes everything in requirements.txt plus sub-dependencies

<pre><code class="language-python"># constraints.txt
black==22.3.0
Brotli==1.0.9
cachetools==5.2.0
certifi==2022.6.15
cffi==1.15.1
...</code></pre>

When used together, we are instructing pip to install everything in requirements.txt with the constraint that if anything is installed that is listed in constraints.txt, use the pinned version.

Now I can be certain sub-dependencies won't break my app without requiring that the sub-dependencies be installed.

July 11, 2022 in [Dev Tools](https://www.jsolly.com/blog/category/dev-tools/)

Updated December 23, 2024