How to freeze requirements that can't be satis

Question

I'm writing a Python app to deploy on Heroku. Per Heroku's guide, I need to list package requirements in a Pip requirements.txt file. The guide instructs me to install the packages locally, then run pip freeze > requirements.txt to write the frozen requirements file.

However, one of the packages I want to use in deployment on Heroku can't be installed locally. It's incompatible with my operating system.

So how do I write a requirements.txt including this package suitable for Heroku?

The only way I can think of is to write it by hand - but this would be tedious, because the package in question has many dependencies of its own. Besides, this defeats the point of the package manager.

---

When deploying Ruby apps to Heroku, Bundler makes this easy. In my Gemfile I write

gem "pg", :group => :production
gem "sqlite3", :group => :development

The command bundle install then writes a frozen version list Gemfile.lock (analogous to requirements.txt). It doesn't install the packages listed under the 'production' group, but it still freezes a consistent list of versioned packages.

Example: Gemfile and Gemfile.lock

Answer 1

It's not possible. Issue reported to pip https://github.com/pypa/pip/issues/747

Answer 2

You can have more than one file, and call them different things, but Heroku does expect a requirements.txt. For instance, for dev, you could maintain a dev_requirements.txt

Locally you can run:

$ pip freeze > dev_requirements.txt

etc, and

$ pip install -r dev_requirements.txt

and Heroku will run:

$ pip install -r requirements.txt