cpython/Mac/OSX

Building and using a framework-based Python on Mac OS X.
--------------------------------------------------------

This document provides a quick introduction to framework-based Python, its
advantages, and how to build it.

1. Why would I want a framework Python instead of a normal static Python?
--------------------------------------------------------------------------

The main reason is because you want to create GUI programs in Python. With the
exception of X11/XDarwin-based GUI toolkits it appears that all GUI programs
need to be run from a fullblown MacOSX application (a ".app" bundle).

While it is technically possible to create a .app without using frameworks you
will have to do the work yourself if you really want this.

A second reason for using frameworks is that they put Python-related items in
only two places: /Library/Framework/Python.framework and /Applications/MacPython-2.3.
This simplifies matters for users installing Python from a binary distribution
if they want to get rid of it again. Moreover, due to the way frameworks work
a user without admin privileges can install a binary distribution in his or
her home directory without recompilation.

Incidentally, the procedure described here is also the procedure that is
used to create the MacPython binary installer, so the information here
should theoretically allow you to rebuild that.

2. How does a framework Python differ from a normal static Python?
------------------------------------------------------------------

In everyday use there is no difference, except that things are stored in
a different place. If you look in /Library/Frameworks/Python.framework
you will see lots of relative symlinks, see the Apple documentation for
details. If you are used to a normal unix Python file layout go down to
Versions/Current and you will see the familiar bin and lib directories.

3. Do I need extra packages?
----------------------------

Yes, probably. If you want to be able to use the PythonIDE you will need to
get Waste, an all-singing-all-dancing TextEdit replacement, from
www.merzwaren.com. It will unpack into a folder named something like "Waste
2.1 Distribution". Make a symlink called "waste" to this folder, somewhere
beside your Python source distribution (it can be "../waste", "../../waste",
etc).

If you want Tkinter support you need to get the OSX AquaTk distribution. If
you want wxPython you need to get that. If you want Cocoa you need to get
pyobjc. Because all these are currently in a state of flux please refer to
http://www.cwi.nl/~jack/macpython.html, which should contain pointers to more
information.

4. How do I build a framework Python?
-------------------------------------

This directory contains a Makefile that will create a couple of python-related
applications (fullblown OSX .app applications, that is) in
/Applications/MacPython-2.3, and a hidden helper application Python.app inside the
Python.framework, and unix tools "python" and "pythonw" into /usr/local/bin.
In addition it has a target "installmacsubtree" that installs the relevant
portions of the Mac subtree into the Python.framework.

It is normally invoked indirectly through the main Makefile, as the last step
in the sequence
1. ./configure --enable-framework
2. make
3. make frameworkinstall

This sequence will put the framework in /Library/Framework/Python.framework,
the applications in /Applications/Python and the unix tools in /usr/local/bin.

Installing in another place, for instance $HOME/Library/Frameworks if you have
no admin privileges on your machine, has only been tested very lightly. This
can be done by configuring with --enable-framework=$HOME/Library/Frameworks.
The other two directories, /Applications/MacPython-2.3 and /usr/local/bin, will then
also be deposited in $HOME. This is sub-optimal for the unix tools, which you
would want in $HOME/bin, but there is no easy way to fix this right now.

Note that there are no references to the actual locations in the code or
resource files, so you are free to move things around afterwards. For example,
you could use --enable-framework=/tmp/newversion/Library/Frameworks and use
/tmp/newversion as the basis for an installer or something.

If you want to install some part, but not all, read the main Makefile. The
frameworkinstall is composed of a couple of sub-targets that install the
framework itself, the Mac subtree, the applications and the unix tools.

There is an extra target frameworkinstallextras that is not part of the
normal frameworkinstall which installs the Demo and Tools directories
into /Applications/MacPython-2.3, this is useful for binary distributions.

If you want to run the Makefile here directly, in stead of through the main
Makefile, you will have to pass various variable-assignments. Read the
beginning of the Makefile for details.


5. What do all these programs do?
---------------------------------

PythonIDE.app is an integrated development environment for Python: editor,
debugger, etc.

PythonLauncher.app is a helper application that will handle things when you
double-click a .py, .pyc or .pyw file. For the first two it creates a Terminal
window and runs the scripts with the normal command-line Python. For the
latter it runs the script in the Python.app interpreter so the script can do
GUI-things. Keep the "alt" key depressed while dragging or double-clicking a
script to set runtime options. These options can be set once and for all
through PythonLauncher's preferences dialog.

BuildApplet.app creates an applet from a Python script. Drop the script on it
and out comes a full-featured MacOS application. There is much more to this,
to be supplied later. Some useful (but outdated) info can be found in
Mac/Demo.

The commandline scripts /usr/local/bin/python and pythonw can be used to run
non-GUI and GUI python scripts from the command line, respectively.

6. How do I create a binary distribution?
-----------------------------------------

First go to Mac/OSX and run "python fixversions.py -a" with the Python
you are going to distribute. This will fix the version numbers and copyright
strings in the various Info.plist files.

Go to the Mac/OSX/Dist directory. There you find a script "build" that
does all the work: it configures and builds a framework Python, installs
it, creates the installer package file and packs this in a DMG image.

All of this is normally done completely isolated in /tmp/_py, so it does not
use your normal build directory nor does it install into /.

Because the build script locates the Python source tree relative to its own
pathname you may have to run it with a full pathname. If you are debugging your
install you can pass one argument: the pathname where the build directory
is located (i.e. where configure and make will be run), then this directory
will be saved between runs of the build script. Do *not* specify your normal
build directory here.

build will ask you whether you have updated the readme file, and it will offer
to include the full documentation in the installer. That option has not
been used for a while, and it may not work.

If you need to execute code on the client machine after installing Python
you can add this to resources/postflight. If you need to do even stranger things
you have to read Apple's documentation on PackageMaker and read the source
of Mac/scripts/buildpkg.py.

7. Odds and ends.
-----------------

The PythonLauncher is actually an Objective C Cocoa app built with Project
Builder. It could be a Python program, except for the fact that pyobjc is not
a part of the core distribution, and is not completely finished yet as of this
writing.

Something to take note of is that the ".rsrc" files in the distribution are
not actually resource files, they're AppleSingle encoded resource files. The
macresource module and the Mac/OSX/Makefile cater for this, and create
".rsrc.df.rsrc" files on the fly that are normal datafork-based resource
files.

	Jack Jansen, Jack.Jansen@cwi.nl, 15-Jul-2004.