Gems against pip

Ruby: Gemfile, gemspec, lock

A Ruby project declares its dependencies in a Gemfile and describes the package itself in a gemspec. The lock file is the resolved answer, and it is committed.

source "https://rubygems.org" gem "minitest", "~> 5.20"

Gem::Specification.new do |spec| spec.name = "calc-demo" spec.version = "0.1.0" spec.summary = "A tiny calculator used by the comparison lessons" spec.authors = ["Arthur Isaev"] spec.files = ["lib/calc.rb"] spec.require_paths = ["lib"] end

bundle install

Fetching gem metadata from https://rubygems.org/...
Resolving dependencies...
Bundle complete! 1 Gemfile dependency, 1 gem now installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.

The lock file records the exact version that Bundler chose:

head -8 Gemfile.lock

GEM
  remote: https://rubygems.org/
  specs:
    minitest (5.27.0)

PLATFORMS
  ruby
  x86_64-linux-musl

Python: pyproject, venv, pip

A Python project declares the package in pyproject.toml and installs it into a virtual environment, which is the Python answer to a per-project gem folder.

[project] name = "calc-demo" version = "0.1.0" description = "A tiny calculator used by the comparison lessons" requires-python = ">=3.9" [build-system] requires = ["setuptools>=68"] build-backend = "setuptools.build_meta"

python3 -m venv .venv

.venv/bin/pip install -e .

Obtaining file:///tmp/vs/pkg
Successfully built calc-demo
Successfully installed calc-demo-0.1.0

-e is the editable install: the environment points at the source folder, so an edit is visible without reinstalling. The Ruby equivalent is bundle exec with the project on the load path, or gem install --local after a build.

.venv/bin/python -c 'import calc_demo; print(calc_demo.VERSION, calc_demo.add(2, 3))'

0.1.0 5

What differs

• Two files against one. Ruby splits the dependency list (Gemfile) from the package description (gemspec). Python puts both into pyproject.toml: the [project] table is the name, the version and the dependencies.
• The environment. Bundler installs into vendor/bundle when told to and into the user gem folder by default. A Python virtual environment is created first and is always local; there is no global default.
• The lock. Gemfile.lock and requirements.txt or a tool that writes a lock (uv, Poetry, pip-tools) play the same role: pin the resolved tree so two machines install the same versions.
• Running. bundle exec rake test versus .venv/bin/python -m pytest: both name the environment explicitly, which is what a pipeline needs.

What to watch for

Commit the lock file of an application and leave it out of a library, in both ecosystems; the same rule, the same reason.

Do not install into the system Ruby or the system Python on a machine you share. A project folder and a lock file are enough to reproduce the environment, and the system stays clean.

Next: Threads in both

Article author: Arthur Isaev