dynamically importing a module and function

[John Machin]

rkmr.em at gmail.com wrote:
> On Mon, Apr 21, 2008 at 3:39 PM, John Machin <sjmachin at lexicon.net> wrote:
>> rkmr.em at gmail.com wrote:
>>> data['module'], in the directory data['cwd']
>>  OT: Any good reason for using a dictionary instead of a class instance
>> (data.functiom, data.module, etc)?
> not really, i just wanted to stick to primitive python data types.
> 
> 
>>> If I do this from python interactive shell (linux fedora core 8) from
>>> dir /home/mark it works fine:
>>>
>>>            cwd = data['cwd']
>>>            os.chdir(cwd)
>>>            print os.getcwd()
>>>            module = __import__(data['module'])
>>>            function = getattr(module, data['function'])
>>>
>>>
> 
>>  saved = sys.path
>>  sys.path = data['cwd']
>>  module = __import__(data['module'])
>>  sys.path = saved
> 
> now the module gets loaded, but i am not able to get the function from
> the module, though it works fine in the interactive-shell
> 
> Traceback (most recent call last):
>   File "/home/mark/work/common/funcq.py", line 62, in <module>
>     if __name__ == '__main__':do()
>   File "/home/mark/work/common/funcq.py", line 35, in do
>     function = getattr(module, data['function'])
> AttributeError: 'module' object has no attribute 'new'
> 
> 
> this works in shell though..
>>>> import os
>>>> os.chdir('/home/mark/work/proj1')
>>>> import sys
>>>> sys.path.append('/home/mark/work/proj1')
>>>> module = __import__('app')
>>>> function = getattr(module, 'new')
>>>> function(1)
> 1

It's not at all obvious that the "works in shell" code is the same as 
the code in your script.

Consider the possibility that as a result of frantic experimentation you 
have multiple copies of app.* with varying contents lying around.

Try this in your script so that you can see exactly what it is doing, 
instead of comparing it to a strawman:
    print "attempting to import", whatever
    module = __import__(whatever)
    print "got", module.__name__, "from", os.path.abspath(module.__file__)
    print "module contents":, dir(module)