Mac/Demo/freezing.html

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   3 <TITLE>Creating standalone applications with Python</TITLE>
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   6 <H1>Creating standalone applications with Python</H1>
   7
   8 With <a href="example2.html#applet">BuildApplet</a> you can build a standalone
   9 Python application that works like
  10 any other Mac application: you can double-click it, run it while the
  11 Python interpreter is running other scripts, drop files on it, etc. It is, however,
  12 still dependent on the whole Python installation on your machine: the PythonCore
  13 engine, the plugin modules and the various Lib folders.<p>
  14
  15 In some cases you may want to create a true application, for instance because
  16 you want to send it off to people who may not have Python installed on their
  17 machine, or because you the application is important and you do not want changes
  18 in your Python installation like new versions to influence it.
  19
  20 <H2>The easy way</H2>
  21
  22 The easiest way to create an application from a Python script is simply by dropping
  23 it on the <code>BuildApplication</code> applet in the main Python folder.
  24 BuildApplication has a similar interface as BuildApplet: you drop a script on
  25 it and it will process it, along with an optional <code>.rsrc</code> file.
  26 It does ask one extra question: whether you want to build your application for
  27 PPC macs only, 68K macs or any Mac.<P>
  28
  29 What BuildApplication does, however, is very different. It parses your script,
  30 recursively looking for all modules you use, bundles the compiled code for
  31 all these modules in PYC resources, adds the executable machine code for the
  32 PythonCore engine, any dynamically loaded modules you use and a main program, combines
  33 all this into a single file and adds a few preference resources (which you
  34 can inspect with <code>EditPythonPrefs</code>, incidentally) to isolate the
  35 new program from the existing Python installation.<P>
  36
  37 Usually you do not need to worry about all this, but occasionally you may have
  38 to exercise some control over the process, for instance because your
  39 program imports modules that don't exist (which can happen if your script
  40 is multi-platform and those modules will never be used on the Mac). See
  41 the section on <a href="#directives">directives</a> below for details.
  42 If you get strange error messages about missing modules it may also be worthwhile
  43 to run macfreeze in report mode on your program, see below.
  44 <P>
  45
  46 <H2>Doing it the hard way</H2>
  47
  48 With the <EM>macfreeze</EM> script, for which BuildApplication is a simple
  49 wrapper, you can go a step further and create CodeWarrior projects and
  50 sourcefiles which can then be used to build your final application. While
  51 BuildApplication is good enough for 90% of the use cases there are situations
  52 where you need macfreeze itself, mainly if you want to embed your frozen Python
  53 script into an existing C application, or when you need the extra bit of speed:
  54 the resulting application will start up a bit quicker than one generated
  55 with BuildApplication. <p>
  56
  57 When you start
  58 <code>Mac:Tools:macfreeze:macfreeze.py</code> you are asked for the
  59 script file, and you can select which type of freeze to do. The first
  60 time you should always choose <em>report only</em>, which will produce a
  61 listing of modules and where they are included from in the console
  62 window. Macfreeze actually parses all modules, so it may crash in the
  63 process. If it does try again with a higher debug value, this should
  64 show you where it crashes. <p>
  65
  66 <h2><a name="directives">Directives</a></h2>
  67
  68 For more elaborate programs you will often see that freeze includes
  69 modules you don't need (because they are for a different platform, for
  70 instance) or that it cannot find all your modules (because you modify
  71 <code>sys.path</code> early in your initialization). It is possible to
  72 include directives to tell macfreeze to add items to the search path and
  73 include or exclude certain modules. All your directives should be in the
  74 main script file. <p>
  75
  76 Directives have the following form:
  77 <pre>
  78 # macfreeze: command argument
  79 </pre>
  80 The trigger <code>macfreeze:</code> must be spelled exactly like that,
  81 but the whitespace can be any combination of spaces and tabs. Macfreeze
  82 understands the following directives:
  83
  84 <DL>
  85 <DT> <code>path</code>
  86 <DD> Prepend a folder to <code>sys.path</code>. The argument is a
  87 pathname, which should probably be relative (starting with a colon) and
  88 is interpreted relative to the folder where the script lives.
  89
  90 <DT> <code>include</code>
  91 <DD> Include a module. The module can either be given by filename or by
  92 module name, in which case it is looked up through the normal method.
  93
  94 <DT> <code>exclude</code>
  95 <DD> Exclude a module. The module must be given by modulename. Even when
  96 freeze deems the module necessary it will not be included in the
  97 application.
  98
  99 <DT> <code>optional</code>
 100 <DD> Include a module if it can be found, but don't complain if it can't.
 101
 102 </DL>
 103
 104 There is actually a fourth way that macfreeze can operate: it can be used
 105 to generate only the resource file containing the compiled <code>PYC</code>
 106 resources. This may be useful if you have embedded Python in your own
 107 application. The resource file generated is the same as for the CodeWarrior
 108 generation process. <p>
 109
 110 <h2>Freezing with CodeWarrior</h2>
 111
 112 To freeze with CodeWarrior you need CodeWarrior, obviously, and a full
 113 source distribution of Python. You select the <em>Codewarrior source and
 114 project</em> option. You specify an output folder, which is by default
 115 the name of your script with <code>.py</code> removed and
 116 <code>build.</code> prepended. If the output folder does not exist yet
 117 it is created, and a template project file and bundle resource file are
 118 deposited there. Next, a source file <code>macfreezeconfig.c</code> is
 119 created which includes all builtin modules your script uses, and a
 120 resource file <code>frozenmodules.rsrc</code> which contains the
 121 <code>PYC</code> resources for all your Python modules. <p>
 122
 123 The project expects to live in a folder one level below the Python root
 124 folder, so the next thing you should do is move the build folder there.
 125 It is a good idea to leave an alias with the same name in the original
 126 location: when you run freeze again it will regenerate the
 127 <code>frozenmodules.rsrc</code> file but not the project and bundle
 128 files. This is probably what you want: if you modify your python sources
 129 you have to re-freeze, but you may have changed the project and bundle
 130 files, so you don't want to regenerate them. <p>
 131
 132 An alternative is to leave the build folder where it is, but then you
 133 have to adapt the search path in the project. <p>
 134
 135 The project is set up to include all the standard builtin modules, but
 136 the CW linker is smart enough to exclude any object code that isn't
 137 referenced. Still, it may be worthwhile to remove any sources for
 138 modules that you are sure are not used to cut back on compilation time.
 139 You may also want to examine the various resource files (for Tcl/Tk, for
 140 instance): the loader has no way to know that these aren't used. <p>
 141
 142 You may also need to add sourcefiles if your script uses non-standard
 143 builtin modules, like anything from the <code>Extensions</code> folder. <p>
 144
 145 The <code>frozenbundle.rsrc</code> resource file contains the bundle
 146 information. It is almost identical to the bundle file used for applets,
 147 with the exception that it sets the <code>sys.path</code> initialization
 148 to <code>$(APPLICATION)</code> only. This means that all modules will only
 149 be looked for in PYC resources in your application. <p>
 150
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