Python Snap Packaging — Core Concepts

What snaps are

Snaps are a universal Linux packaging format created by Canonical. A snap is a compressed SquashFS filesystem image containing your application, its runtime dependencies, and metadata. When installed, the snap is mounted read-only and runs in a sandboxed environment with controlled access to system resources.

For Python developers, snaps solve the “but it works on my machine” problem by bundling a specific Python version and all pip dependencies into a single distributable package.

The snapcraft.yaml file

Every snap project needs a snapcraft.yaml that describes how to build and package the application:

name: my-python-app
version: '1.0.0'
summary: A useful Python CLI tool
description: |
  A longer description of what the tool does,
  displayed in the Snap Store listing.
  
grade: stable          # or 'devel' for pre-release
confinement: strict    # sandboxed (recommended for store)
base: core22           # Ubuntu 22.04 runtime

apps:
  my-python-app:
    command: bin/my-python-app
    plugs:
      - network        # Allow network access
      - home           # Allow access to ~/

parts:
  my-python-app:
    plugin: python
    source: .
    python-packages:
      - requests
      - click

Build the snap:

# Install snapcraft
sudo snap install snapcraft --classic

# Build
snapcraft

# Output: my-python-app_1.0.0_amd64.snap

How the Python plugin works

Snapcraft’s python plugin automates Python packaging:

1. Installs Python from the base snap (core22 includes Python 3.10).
2. Creates a virtual environment inside the snap.
3. Installs your package using pip (reads setup.py, pyproject.toml, or explicit python-packages).
4. Bundles everything into the snap’s filesystem.

For projects using pyproject.toml:

parts:
  my-app:
    plugin: python
    source: .
    # Automatically reads pyproject.toml and installs the project

For requirements.txt-based projects:

parts:
  my-app:
    plugin: python
    source: .
    python-requirements:
      - requirements.txt

Confinement and interfaces

Snaps run in a security sandbox. Your app gets access to resources through interfaces (called plugs and slots):

Interface	What it allows
network	Outbound network connections
network-bind	Listen on ports (servers)
home	Read/write to the user’s home directory
removable-media	Access USB drives and mounted media
desktop	Desktop integration (icons, notifications)
x11	Display windows using X11

apps:
  my-server:
    command: bin/my-server
    daemon: simple          # Run as a background service
    plugs:
      - network
      - network-bind

Three confinement levels:

• strict — full sandbox. Required for Snap Store publishing.
• devmode — sandbox violations are logged but allowed. Good for development.
• classic — no sandbox, full system access. Requires Snap Store approval.

Publishing to the Snap Store

# Register your snap name
snapcraft register my-python-app

# Login
snapcraft login

# Upload and release
snapcraft upload my-python-app_1.0.0_amd64.snap --release=stable

The Snap Store supports channels for release management:

• edge — latest commits, possibly broken.
• beta — feature-complete but not fully tested.
• candidate — release candidate.
• stable — production-ready.

Users install from a channel:

sudo snap install my-python-app                    # stable (default)
sudo snap install my-python-app --channel=beta     # beta

Automatic updates

One of snaps’ strongest features: automatic background updates. When you push a new version to the Snap Store, all installed instances update automatically within a few hours. Users do not need to do anything.

If an update causes problems, snaps support automatic rollback — the system reverts to the previous version.

When snaps make sense for Python apps

Good use cases:

• CLI tools you want to distribute broadly on Linux.
• Background services (daemons) that need auto-updates.
• Desktop applications with GUI that need system integration.
• DevOps tools deployed across many Linux servers.

Less ideal for:

• Libraries — snaps are for applications, not importable packages (use PyPI for those).
• macOS/Windows — snaps are Linux-only.
• Minimal containers — Docker images are better for container-native deployments.

Common misconception

“Snaps are just like Docker containers.”

While both provide isolation, they serve different purposes. Docker containers are for server workloads and typically run headless services. Snaps are for end-user software — they integrate with the desktop, appear in app launchers, handle auto-updates, and work with the user’s filesystem. A snap can be a GUI app, a CLI tool, or a daemon, all with desktop integration that Docker does not provide.

One thing to remember: Snaps give Python developers a path to distributing self-contained, auto-updating Linux applications through the Snap Store — with sandboxing that protects both the user’s system and your app from dependency conflicts.