The answer

Sun Jan 17 22:57:00 EST 2010

* Jive Dadson:
> Okay, with your help I've figured it out.  Instructions are below, but 
> read the caveat by Ben Fenny in this thread.  All this stuff is good for 
> one default version of Python only.  The PYTHONPATH described below, for 
> example, cannot specify a version number.  Yes, that's a pain in the 
> butt, but there's no way around it.  If you switch versions, you may 
> have to delete all the .pyc files that will show up in the module 
> folders.  Python ought to check them to see if they are valid, but I do 
> not know if it does so.
> 
> These instructions are for MS Windows.
> 
> 1) Create your modules folder. Let's say it's named "Modules."  The 
> documentation calls it a "package."
> 
> 2) In an explorer window or on the desktop, right click on My Computer, 
> and select Properties.
> 
> 3) Select the Advanced tab, and click on Environment Variables near the 
> bottom.
> 
> 4) Look for an environment variable named PYTHONPATH.
> 
>    a) If you do not find one, create one using the New button(s). I 
> don't know if it has to be in User Variables or System Variables.  To 
> save time experimenting, I just put one in both. For the value, put the 
> full path of the folder Modules.

The User variables /override/ the System variables for a given user. The System 
variables provide defaults for all users. One notable exception is PATH, where 
the User PATH items are appended to the System PATH.

Anyways, with many items in a variable like PATH it can be impractical to use 
Windows' functionality, which presents it all on one line, which for a PATH with 
many items can be exceeding long  --  like a many thousand characters[1] line.

So for your convenience, below is a little Windows app (as an HTML application, 
it's just some HTML and VBScript and CSS) that presents the user PATH items one 
per line in a Notepad-like window. It should be no problem modifying it to 
instead edit PYTHONPATH, or even a choice of environment variable. As my late 
father used to say, when you don't have a tool, you make it.

Maybe now I should recode this in Python. But on the other hand, one shouldn't 
spend time fixing what works.  So  ... enjoy! :-)

Note: it's crucial to use [.HTA] filename extension.
Also, it's quite possible that this doesn't work in Windows Vista (at least not 
without configuration of Windows), but it works in XP and earlier.

<code file="userpath.hta">
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Strict//EN">
<!-- If this works, then it was written by Alf P. Steinbach.
      Otherwise it's someone impersonating me.
      And yes, if you've seen a comment like this before: I/he stole it. :-) -->
<html>
     <head>
         <meta name=vs_targetSchema 
content="http://schemas.microsoft.com/intellisense/ie5">
         <meta http-equiv="content-type" content="text/html; charset=iso-8859-1">
         <meta http-equiv="MSThemeCompatible" content="yes">

         <hta:application scroll="no"/>
         <title>Simple user-environment %path% editor</title>

         <style>
             body        { margin: 0px; padding: 0px; }

             #menuArea
             {
                 width: 100%; height: 1.8em; white-space: nowrap; padding-top: 2px;
                 background: #E0E0E0;
             }

             #clientArea
             {
                 width: 100%; position: absolute; top: 1.8em; bottom: 0;
             }

             #pathEditor
             {
                 display: inline-block;
                 width: 100%; height: 100%;
                 border: 0;
                 position: absolute; top: 0;
                 overflow: scroll;
             }
         </style>

         <script type="text/vbscript" language="vbscript">
             option explicit
             dim wshShell
             dim wshUserEnv
             dim originalText

             sub loadText
                 pathEditor.innerText = replace( wshUserEnv( "PATH" ), ";", 
vbNewline)
             end sub

             sub saveText
                 dim text
                 dim button

                 text = pathEditor.innerText
                 text = replace( text, vbNewLine, ";" )
                 button = MsgBox( _
                     text, vbYesNo + vbQuestion, "Save this as new %path% value?" _
                     )
                 if button = vbYes then wshUserEnv( "PATH" ) = text
             end sub

             sub onBtnLoad
                 loadText
             end sub

             sub onBtnLoadOriginal
                 pathEditor.innerText = originalText
             end sub

             sub onBtnSave
                 saveText
             end sub

             sub onLoaded
                 set wshShell = createObject( "WScript.Shell" )
                 set wshUserEnv = wshShell.environment( "USER" )
                 loadText
                 originalText = pathEditor.innerText
                 MsgBox _
                     "Type one path per line (no semicolons)", _
                     vbInformation, _
                     "How to use:"
             end sub
         </script>
     </head>

     <body onload="onLoaded">
         <div id="menuArea">
               <button onClick="onBtnLoad">Load current</button>
               <button onClick="onBtnLoadOriginal">Reload original</button>
               <button onClick="onBtnSave">Save as current ...</button>
         </div>
         <div id="clientArea">
             <textarea id="pathEditor" wrap="off">
             </textarea>
         </div>
     </body>
</html>
</code>

>    b) If there's already a PYTHONPATH,  Edit it, adding a semi-colon and 
> the full path of folder Module to the end.
> 
> 5) Put your module folders into the folder Module.
> 
> 6) (Here's a really arcane bit.) Into each module folder, put a file 
> named __init__.py.  It will be executed when you load the module.  It 
> can be empty, but it has to be there or else the module folder will be 
> ignored.

Cheers & hth.,

- Alf

Notes:
[1] Windows XP and I believe also Vista places a limit of about 8 KiB on the 
length of any environment variable.