Monthly Archives: 2011-2

Changing the active Python interpreter on Windows

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2

A lot of Windows Python software use wrapper .exe files which pick the Python interpreter  based on this registry settings. One notable exe is buildout.exe, which is used to run buildout.

If you install multiple Pythons, the latter installations might not become active in the registry automatically, and your Python wrapper still rely on the old version. This leads to version incompatibilities and you are unable to start the Python applications.

Since only one Python interpreter can be activate at a time, it is little bit difficult to develop multi-version Python code Windows. This kind of situation could be that you develop Plone 3 sites (Python 2.4) and Plone 4 sites (Python 2.6) simultaneously.

Below is regpy.py code which changes the active Python interpreter. The orignal author is unknown, I picked up this code from some paste board long time ago. Just run this code with your Python and the running interpreter becomes active.

Example how to activate alternative Python interpreter:

C:\Plone\python\python.exe regpy.py

regpy.py:

import sys

from _winreg import *

# tweak as necessary
version = sys.version[:3]
installpath = sys.prefix

regpath = "SOFTWARE\\Python\\Pythoncore\\%s\\" % (version)
installkey = "InstallPath"
pythonkey = "PythonPath"
pythonpath = "%s;%s\\Lib\\;%s\\DLLs\\" % (
    installpath, installpath, installpath
)

def RegisterPy():
    try:
        reg = OpenKey(HKEY_LOCAL_MACHINE, regpath)
    except EnvironmentError:
        try:
            reg = CreateKey(HKEY_LOCAL_MACHINE, regpath)
            SetValue(reg, installkey, REG_SZ, installpath)
            SetValue(reg, pythonkey, REG_SZ, pythonpath)
            CloseKey(reg)
        except:
            print "*** Unable to register!"
            return
        print "--- Python", version, "is now registered!"
        return
    if (QueryValue(reg, installkey) == installpath and
        QueryValue(reg, pythonkey) == pythonpath):
        CloseKey(reg)
        print "=== Python", version, "is already registered!"
        return
    CloseKey(reg)
    print "*** Unable to register!"
    print "*** You probably have another Python installation!"

if __name__ == "__main__":
    RegisterPy()

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Searching arbitary HTML snippets on Plone content pages

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5

Here is an example how to crawl through Plone content to search HTML snippets. This can be done by rendering every content object and check whether certain substrings exists the output HTML This snippet can be executed through-the-web in Zope Management Interface.

This kind of scripting is especially useful if you need to find old links or migrate some text / HTML snippets in the content itself. There might be artifacts which only appear on the resulting pages (portlets, footer texts, etc.) and thus they are invisible to the normal full text search.

# Find arbitary HTML snippets on Plone content pages 

# Collect script output as text/html, so that you can
# call this script conveniently by just typing its URL to a web browser
buffer = ""

# We need to walk through all the content, as the
# links might not be indexed in any search catalog
for brain in context.portal_catalog(): # This queries cataloged brain of every content object
       try:
         obj = brain.getObject()
         # Call to the content object will render its default view and return it as text
         # Note: this will be slow - it equals to load every page from your Plone site
         rendered = obj()
         if "yourtextmatch" in rendered:
               # found old link in the rendered output
               buffer += "Found old links on <a href='%s'>%s</a><br>\n" % (obj.absolute_url(), obj.Title())
       except:
         pass # Something may fail here if the content object is broken

return buffer

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