[Python-Dev] PEP 4XX: pyzaa "Improving Python ZIP Application Support"

Daniel Holth dholth at gmail.com
Tue Apr 2 02:47:08 CEST 2013



Title: Improving Python ZIP Application Support

Author: Daniel Holth <dholth at gmail.com>

Status: Draft

Type: Standards Track

Python-Version: 3.4

Created: 30 March 2013

Post-History: 30 March 2013, 1 April 2013

Improving Python ZIP Application Support

Python has had the ability to execute directories or ZIP-format
archives as scripts since version 2.6. When invoked with a zip file or
directory as its first argument the interpreter adds that directory to
sys.path and executes the __main__ module. These archives provide a
great way to publish software that needs to be distributed as a single
file script but is complex enough to need to be written as a
collection of modules.

This feature is not as popular as it should be, mainly because no
one’s heard of it because it wasn’t promoted as part of Python 2.6,
but also because Windows users don’t have a file extension (other than
.py) to associate with the launcher.

This PEP proposes to fix these problems by re-publicising the feature,
defining the .pyz and .pyzw extensions as “Python ZIP Applications”
and “Windowed Python ZIP Applications”, and providing some simple
tooling to manage the format.

A New Python ZIP Application Extension

The Python 3.4 installer will associate .pyz and .pyzw “Python ZIP
Applications” with the platform launcher so they can be executed. A
.pyz archive is a console application and a .pyzw archive is a
windowed application, indicating whether the console should appear
when running the app.

Why not use .zip or .py? Users expect a .zip file would be opened with
an archive tool, and users expect .py to be opened with a text editor.
Both would be confusing for this use case.

For UNIX users, .pyz applications should be prefixed with a #! line
pointing to the correct Python interpreter and an optional

#!/usr/bin/env python3

# This is a Python application stored in a ZIP archive.

(binary contents of archive)

As background, ZIP archives are defined with a footer containing
relative offsets from the end of the file. They remain valid when
concatenated to the end of any other file. This feature is completely
standard and is how self-extracting ZIP archives and the bdist_wininst
installer format work.

Minimal Tooling: The pyzaa Module

This PEP also proposes including a simple application for working with
these archives: The Python Zip Application Archiver “pyzaa” (rhymes
with “huzzah” or “pizza”). “pyzaa” can archive or extract these files,
compile bytecode, and can write the __main__ module if it is not


python -m pyzaa (pack | compile)

python -m pyzaa pack [-o path/name] [-m module.submodule:callable]
[-c] [-w] [-p interpreter] directory:

    ZIP the contents of directory as directory.pyz or [-w]
directory.pyzw. Adds the executable flag to the archive.

    -c compile .pyc files and add them to the archive

    -p interpreter include #!interpreter as the first line of the archive

    -o path/name archive is written to path/name.pyz[w] instead of
dirname. The extension is added if not specified.

    -m module.submodule:callable __main__.py is written as “import
module.submodule; module.submodule.callable()”

    pyzaa pack will warn if the directory contains C extensions or if
it doesn’t contain __main__.py.

python -m pyzaa compile arcname.pyz[w]

    The Python files in arcname.pyz[w] are compiled and appended to
the ZIP file.

A standard ZIP utility or Python’s zipfile module can unpack the archives.


Q. Isn’t pyzaa just a very thin wrapper over zipfile and compileall?

A. Yes.

Q. How does this compete with existing sdist/bdist formats?

A. There is some overlap, but .pyz files are especially interesting as
a way to distribute an installer. They may also prove useful as a way
to deliver applications when users shouldn’t be asked to perform
virtualenv + “pip install”.


[1] http://bugs.python.org/issue1739468 “Allow interpreter to execute
a zip file”

[2] http://bugs.python.org/issue17359 “Feature is not documented”


This document has been placed into the public domain.

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