dynamically importing a module and function

[rkmr.em@gmail.com]

Hi
I have a function data['function'], that I need to import from a file
data['module'], in the directory data['cwd']

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'])

But if I put this in a file /home/mark/work/common/funcq.py and run it
from /home/mark, it throws me error like this.. how to fix this? it
imports the module successfully, but it is not looking for subsequent
modules in the os.getcwd()..

/home/mark/work/proj1
Traceback (most recent call last):
File "/home/mark/work/common/funcq.py", line 60, in <module>
if __name__ == '__main__':do()
File "/home/mark/work/common/funcq.py", line 33, in do
module = __import__(data['module'])
File "/home/mark/app.py", line 5, in <module>
import abcde
ImportError: No module named abcde

[John Machin]

Re: dynamically importing a module and function

rkmr.em@gmail.c om wrote:

Hi
I have a function data['function'], that I need to import from a file
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)?

>
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'])
>

This is possibly due to python using what was the current working
directory when it started up.

An alternative (untested):

saved = sys.path
sys.path = data['cwd']
module = __import__(data['module'])
sys.path = saved

Exception handling is left as an exercise for the reader.

HTH,
John

[rkmr.em@gmail.com]

Re: dynamically importing a module and function

On Mon, Apr 21, 2008 at 3:39 PM, John Machin <sjmachin@lexic on.netwrote:

rkmr.em@gmail.c om 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.appe nd('/home/mark/work/proj1')
>>module = __import__('app ')
>>function = getattr(module, 'new')
>>function(1)

1

[John Machin]

Re: dynamically importing a module and function

rkmr.em@gmail.c om wrote:

On Mon, Apr 21, 2008 at 3:39 PM, John Machin <sjmachin@lexic on.netwrote:

>rkmr.em@gmail.c om 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.app end('/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__(what ever)
print "got", module.__name__ , "from", os.path.abspath (module.__file_ _)
print "module contents":, dir(module)

[rkmr.em@gmail.com]

Re: dynamically importing a module and function

On Mon, Apr 21, 2008 at 4:47 PM, John Machin <sjmachin@lexic on.netwrote:

saved = sys.path
sys.path = data['cwd']
module = __import__(data['module'])
sys.path = saved
>
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.

thanks a lot!
there was a file app.pyc lying around in the dir from which i was
running the script...