Ad:

Python Discussion Thread
Marked Solved
Views: 6670

Aug 10th, 2005

getattr function

Expand Post »

hello fellows,

I seem to have a little problem:

I tried to use the function getattr(object, attribute) with two strings which is being read from a xml file as arguments, and seem to have a problem with sending the first one as a string. the function thinks that the string object itself is the object argument, when what i meant was that the VALUE of my string will be sent to the function as a name of a module in my program.

the second argument however, isn't doing any problems, and is being treated as the object of the value of the string, and not as a string object itself.
weird!

maybe a conversion between a string object and a module object is possible? i don't know...

help?

Similar Threads

getattr function 2 in Python
Function that returns void in C++

Avner .H.

Reputation Points: 10

Solved Threads: 0

Newbie Poster

Offline

18 posts
since Aug 2005

Permalink

Aug 11th, 2005

Re: getattr function

Would be nice to have an actual example!

Check the "mimic a C struct type with an empty Python class " in the Starting Python sticky. You could do something along that line.

vegaseat

Moderator

Reputation Points: 1333

Solved Threads: 1403

DaniWeb's Hypocrite

Offline

5,792 posts
since Oct 2004

Permalink

Aug 11th, 2005

Re: getattr function

Hmm. Here's one way around it, using exec() instead of getattr():

Python Syntax (Toggle Plain Text)
import sys
# For our example, let's use random.sample() as the desired attribute
# This function takes as input a list and an integer n and returns a
# random, non-redundant selection of n elements from the list
modname = "random"
attname = "sample"
# Import the module using exec, set the function to a wrapper variable
exec("import "+modname)
exec("sampleWrapper = "+modname+"."+attname)
# Test the wrapper variable
print sampleWrapper([1, 2, 3, 4, 5, 6], 2)
import sys
# For our example, let's use random.sample() as the desired attribute
# This function takes as input a list and an integer n and returns a
# random, non-redundant selection of n elements from the list
modname = "random"
attname = "sample"
# Import the module using exec, set the function to a wrapper variable
exec("import "+modname)
exec("sampleWrapper = "+modname+"."+attname)
# Test the wrapper variable
print sampleWrapper([1, 2, 3, 4, 5, 6], 2)

Something more in line with what you were thinking of might be:

Python Syntax (Toggle Plain Text)
exec("import "+modname)
exec("mod = "+modname)
# Now we can use mod as though it were the actual module
sampleWrapper = getattr(mod, "sample")
print sampleWrapper([1, 2, 3, 4, 5, 6], 2)
exec("import "+modname)
exec("mod = "+modname)
# Now we can use mod as though it were the actual module
sampleWrapper = getattr(mod, "sample")
print sampleWrapper([1, 2, 3, 4, 5, 6], 2)

It's tricky, but it works!

G-Do

Reputation Points: 41

Solved Threads: 31

Junior Poster

Offline

146 posts
since Jun 2005

Permalink

Aug 11th, 2005

Re: getattr function

Neat! Never thought of exec() that way!

vegaseat

Moderator

Reputation Points: 1333

Solved Threads: 1403

DaniWeb's Hypocrite

Offline

5,792 posts
since Oct 2004

Permalink

Aug 15th, 2005

Re: getattr function

Cool!
Thanks very much!

Avner .H.

Reputation Points: 10

Solved Threads: 0

Newbie Poster

Offline

18 posts
since Aug 2005

Permalink

Sep 14th, 2005

Re: getattr function

Quote originally posted by Avner .H. ...

hello fellows,

I seem to have a little problem:

I tried to use the function getattr(object, attribute) with two strings which is being read from a xml file as arguments, and seem to have a problem with sending the first one as a string. the function thinks that the string object itself is the object argument, when what i meant was that the VALUE of my string will be sent to the function as a name of a module in my program.

the second argument however, isn't doing any problems, and is being treated as the object of the value of the string, and not as a string object itself.
weird!

maybe a conversion between a string object and a module object is possible? i don't know...

help?

Try

Python Syntax (Toggle Plain Text)
fn = getattr(__import__('example_module'), 'example_function')
fn = getattr(__import__('example_module'), 'example_function')

The getattr builtin requires the module object, therefore you have to load that module using __import__() first.

kerumai

Reputation Points: 10

Solved Threads: 1

Newbie Poster

Offline

1 posts
since Sep 2005

This thread is solved

Either the thread starter or a moderator has marked this thread as solved. You can most likely trust the responses and answers given. There is most likely no reason for any further responses to be posted here. If you have a related question, please start a new thread in this forum instead.

This thread is more than three months old

No one has posted to this discussion for at least three months. Please let old threads die and do not reply to them unless you feel you have something new and valuable to contribute that absolutely must be added to make the discussion complete. Otherwise, please start a new thread in this forum instead.

Previous Thread in Python Forum Timeline: Random Graphics (Python)

Next Thread in Python Forum Timeline: Python's Debugger

DaniWeb Message

Cancel Changes

User Name
Password