zipapp — Manage executable python zip archives

Source code: Lib/zipapp.py

This module provides tools to manage the creation of zip files containing Python code, which can be executed directly by the Python interpreter. The module provides both a Command-Line Interface and a Python API.

1. Basic Example

The following example shows how the Command-Line Interface can be used to create an executable archive from a directory containing Python code. When run, the archive will execute the main function from the module myapp in the archive.

$ python -m zipapp myapp -m "myapp:main"
$ python myapp.pyz
<output from myapp>

2. Command-Line Interface

When called as a program from the command line, the following form is used:

$ python -m zipapp source [options]

If source is a directory, this will create an archive from the contents of source. If source is a file, it should be an archive, and it will be copied to the target archive (or the contents of its shebang line will be displayed if the –info option is specified).

The following options are understood:

-o <output>, --output=<output>

Write the output to a file named output. If this option is not specified, the output filename will be the same as the input source, with the extension .pyz added. If an explicit filename is given, it is used as is (so a .pyz extension should be included if required).

An output filename must be specified if the source is an archive (and in that case, output must not be the same as source).

-p <interpreter>, --python=<interpreter>

Add a #! line to the archive specifying interpreter as the command to run. Also, on POSIX, make the archive executable. The default is to write no #! line, and not make the file executable.

-m <mainfn>, --main=<mainfn>

Write a __main__.py file to the archive that executes mainfn. The mainfn argument should have the form “pkg.mod:fn”, where “pkg.mod” is a package/module in the archive, and “fn” is a callable in the given module. The __main__.py file will execute that callable.

--main cannot be specified when copying an archive.

--info

Display the interpreter embedded in the archive, for diagnostic purposes. In this case, any other options are ignored and SOURCE must be an archive, not a directory.

-h, --help

Print a short usage message and exit.

3. Python API

The module defines two convenience functions:

zipapp.create_archive(source, target=None, interpreter=None, main=None)

Create an application archive from source. The source can be any of the following:

• The name of a directory, or a pathlib.Path object referring to a directory, in which case a new application archive will be created from the content of that directory.
• The name of an existing application archive file, or a pathlib.Path object referring to such a file, in which case the file is copied to the target (modifying it to reflect the value given for the interpreter argument). The file name should include the .pyz extension, if required.
• A file object open for reading in bytes mode. The content of the file should be an application archive, and the file object is assumed to be positioned at the start of the archive.

The target argument determines where the resulting archive will be written:

• If it is the name of a file, or a pathlb.Path object, the archive will be written to that file.
• If it is an open file object, the archive will be written to that file object, which must be open for writing in bytes mode.
• If the target is omitted (or None), the source must be a directory and the target will be a file with the same name as the source, with a .pyz extension added.

The interpreter argument specifies the name of the Python interpreter with which the archive will be executed. It is written as a “shebang” line at the start of the archive. On POSIX, this will be interpreted by the OS, and on Windows it will be handled by the Python launcher. Omitting the interpreter results in no shebang line being written. If an interpreter is specified, and the target is a filename, the executable bit of the target file will be set.

The main argument specifies the name of a callable which will be used as the main program for the archive. It can only be specified if the source is a directory, and the source does not already contain a __main__.py file. The main argument should take the form “pkg.module:callable” and the archive will be run by importing “pkg.module” and executing the given callable with no arguments. It is an error to omit main if the source is a directory and does not contain a __main__.py file, as otherwise the resulting archive would not be executable.

If a file object is specified for source or target, it is the caller’s responsibility to close it after calling create_archive.

When copying an existing archive, file objects supplied only need read and readline, or write methods. When creating an archive from a directory, if the target is a file object it will be passed to the zipfile.ZipFile class, and must supply the methods needed by that class.

zipapp.get_interpreter(archive)

Return the interpreter specified in the #! line at the start of the archive. If there is no #! line, return None. The archive argument can be a filename or a file-like object open for reading in bytes mode. It is assumed to be at the start of the archive.

4. Examples

Pack up a directory into an archive, and run it.

$ python -m zipapp myapp
$ python myapp.pyz
<output from myapp>

The same can be done using the create_archive() functon:

>>> import zipapp
>>> zipapp.create_archive('myapp.pyz', 'myapp')

To make the application directly executable on POSIX, specify an interpreter to use.

$ python -m zipapp myapp -p "/usr/bin/env python"
$ ./myapp.pyz
<output from myapp>

To replace the shebang line on an existing archive, create a modified archive using the create_archive() function:

>>> import zipapp
>>> zipapp.create_archive('old_archive.pyz', 'new_archive.pyz', '/usr/bin/python3')

To update the file in place, do the replacement in memory using a BytesIO object, and then overwrite the source afterwards. Note that there is a risk when overwriting a file in place that an error will result in the loss of the original file. This code does not protect against such errors, but production code should do so. Also, this method will only work if the archive fits in memory:

>>> import zipapp
>>> import io
>>> temp = io.BytesIO()
>>> zipapp.create_archive('myapp.pyz', temp, '/usr/bin/python2')
>>> with open('myapp.pyz', 'wb') as f:
>>>     f.write(temp.getvalue())

Note that if you specify an interpreter and then distribute your application archive, you need to ensure that the interpreter used is portable. The Python launcher for Windows supports most common forms of POSIX #! line, but there are other issues to consider:

• If you use “/usr/bin/env python” (or other forms of the “python” command, such as “/usr/bin/python”), you need to consider that your users may have either Python 2 or Python 3 as their default, and write your code to work under both versions.
• If you use an explicit version, for example “/usr/bin/env python3” your application will not work for users who do not have that version. (This may be what you want if you have not made your code Python 2 compatible).
• There is no way to say “python X.Y or later”, so be careful of using an exact version like “/usr/bin/env python3.4” as you will need to change your shebang line for users of Python 3.5, for example.

5. The Python Zip Application Archive Format

Python has been able to execute zip files which contain a __main__.py file since version 2.6. In order to be executed by Python, an application archive simply has to be a standard zip file containing a __main__.py file which will be run as the entry point for the application. As usual for any Python script, the parent of the script (in this case the zip file) will be placed on sys.path and thus further modules can be imported from the zip file.

The zip file format allows arbitrary data to be prepended to a zip file. The zip application format uses this ability to prepend a standard POSIX “shebang” line to the file (#!/path/to/interpreter).

Formally, the Python zip application format is therefore:

1. An optional shebang line, containing the characters b'#!' followed by an interpreter name, and then a newline (b'\n') character. The interpreter name can be anything acceptable to the OS “shebang” processing, or the Python launcher on Windows. The interpreter should be encoded in UTF-8 on Windows, and in sys.getfilesystemencoding() on POSIX.
2. Standard zipfile data, as generated by the zipfile module. The zipfile content must include a file called __main__.py (which must be in the “root” of the zipfile - i.e., it cannot be in a subdirectory). The zipfile data can be compressed or uncompressed.

If an application archive has a shebang line, it may have the executable bit set on POSIX systems, to allow it to be executed directly.

There is no requirement that the tools in this module are used to create application archives - the module is a convenience, but archives in the above format created by any means are acceptable to Python.