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