Finding missing dependencies in distributed ArcGIS Python toolbox?

Question

I am developing a Python Toolbox that uses a few external libraries (ogr/gdal, matplotlib, shapely, reportlab among others) which files I have directly copied in the same folder as my toolbox .py, as recommended in Esri's A simple approach for including 3rd party Python libraries with your scripts. It works just fine on my computer, but when I run this tool on another computer, I get an ImportError. It's very likely that the libraries are the reason for that error.

<type 'exceptions.ImportError'>: DLL load failed: The specified procedure could not be found.

Moreover, I don't get the ImportError the same way from ArcGIS10.0 or ArcGIS10.1 (10.0: only get the error without any additional message; 10.1: get the error where it worked fine in the previous version), which worries me a bit because this really looks like a singular configuration dependent problem.

How do I find the missing dependencies in my current distribution and ensure that the tool which I distribute will work on every computer with a fresh ArcGIS installation?

I have tried what I consider the usual ways to solve that problem:

• Run the script outside ArcMap to debug it but I did not get much more information.
• Use Dependency Walker to find the missing DLLs but when I try to profile ArcMap, Dependency Walker stops running.

Answer 1

I don't think this is a matter of missing dependencies, it's a matter of incorrectly versioned dependencies. ArcGIS 10.0 runs Python 2.6, while 10.1 runs 2.7. Any library with a C extension will need to be bundled with your toolbox for the correct version of Python depending on the target version of ArcGIS.