IronPython 1.0 - Bugs or Features?

[Larry Bates]

Claudio Grondi wrote:
> (just wanted to share my experience with IronPython 1.0)
> 
> The context:
>   C:\IronPython> ipy.exe
>   IronPython 1.0.60816 on .NET 2.0.50727.42
>   Copyright (c) Microsoft Corporation. All rights reserved.
> vs.
>   C:\Python24> python.exe
>   Python 2.4.2 (#67, Sep 28 2005, 12:41:11) [MSC v.1310 32 bit (Intel)]
> on win32
> 
> IronPython raises "UnboundLocalError: local variable 'strData'
> referenced before assignment" error in following case:
> <code>
>     while(someCondition):
>       try:
>         strData = strSomeValue()
>       except:
>         pass
>       if( type(strData) == str ) : ### <<< HERE THE ERROR
>         doSomething()
> </code>
> CPython 2.4.2 doesn't raise an error with same code.
> 
> As strData is not set anywhere before in the code it seems, that
> IronPython is somehow right, but I am not sure if it is a bug or a feature.
> 
> Another problem with IronPython where CPython 2.4.2 runs ok was while I
> was trying to do:
>   f = file(r'\\.\PhysicalDrive0', 'rb')
> getting "ValueError: FileStream will not open Win32 devices such as disk
> partitions and tape drives. Avoid use of "\\.\" in the path."
> Here the same - I am not sure if it is a bug or a feature.
> 
> Can someone knowledgeable elaborate on it a bit please?
> 
> Claudio Grondi

Your problem is a blanket exception handler that ignores
the exception.  Blanket exceptions are almost always a
bad idea.  Blanket exceptions with pass as the only
command in the except: block is ALWAYS a bad idea.

Basically the line strData = strSomeValue() caused an
exception.  Since it was inside a try: block, it then
executed what was in the except: block.  Since all that
was in the except: block was pass, it just fell through
to the if statement.  At that point strData is not
defined because the try block failed and never create
strData object.

It is doing EXACTLY what you told it to do.

-Larry Bates