Dropping a file onto a script to run as argument causes exception in Vista

Question

edit:OK, I could swear that the way I'd tested it showed that the getcwd was also causing the exception, but now it appears it's just the file creation. When I move the try-except blocks to their it actually does catch it like you'd think it would. So chalk that up to user error.
Original Question:
I have a script I'm working on that I want to be able to drop a file on it to have it run with that file as an argument. I checked in this question, and I already have the mentioned registry keys (apparently the Python 2.6 installer takes care of it.) However, it's throwing an exception that I can't catch. Running it from the console works correctly, but when I drop a file on it, it throws an exception then closes the console window. I tried to have it redirect standard error to a file, but it threw the exception before the redirection occurred in the script. With a little testing, and some quick eyesight I saw that it was throwing an IOError when I tried to create the file to write the error to.

import sys
import os

#os.chdir("C:/Python26/Projects/arguments")
try:
    print sys.argv
    raw_input()
    os.getcwd()
except Exception,e:
    print sys.argv + '\n'
    print e
f = open("./myfile.txt", "w")

If I run this from the console with any or no arguments, it behaves as one would expect. If I run it by dropping a file on it, for instance test.txt, it runs, prints the arguments correctly, then when os.getcwd() is called, it throws the exception, and does not perform any of the stuff from the except: block, making it difficult for me to find any way to actually get the exception text to stay on screen. If I uncomment the os.chdir(), the script doesn't fail. If I move that line to within the except block, it's never executed.

I'm guessing running by dropping the file on it, which according to the other linked question, uses the WSH, is somehow messing up its permissions or the cwd, but I don't know how to work around it.

Answer 1

Seeing as this is probably not Python related, but a Windows problem (I for one could not reproduce the error given your code), I'd suggest attaching a debugger to the Python interpreter when it is started. Since you start the interpreter implicitly by a drag&drop action, you need to configure Windows to auto-attach a debugger each time Python starts. If I remember correctly, this article has the needed information to do that (you can substitute another debugger if you are not using Visual Studio).

Apart from that, I would take a snapshot with ProcMon while dragging a file onto your script, to get an idea of what is going on.

Answer 2

As pointed out in my edit above, the errors were caused by the working directory changing to C:\windows\system32, where the script isn't allowed to create files. I don't know how to get it to not change the working directory when started that way, but was able to work around it like this.

if len(sys.argv) == 1:
    files = [filename for filename in os.listdir(os.getcwd())
             if filename.endswith(".txt")]
else:
    files = [filename for filename in sys.argv[1:]]

Fixing the working directory can be managed this way I guess.

exepath = sys.argv[0]    
os.chdir(exepath[:exepath.rfind('\\')])