Wednesday, June 18, 2014

Finding the Location of Your Python File

Another issue I have run into depending on the OS, is the ability to find where the python file is located that is being run.  I like the use the __file__ property, but it's not always present.  Thanks to google, I found this:

__file__ is the path name of the file from which the module was loaded, if it was loaded from a file. The __file__ attribute is not present for C modules that are statically linked into the interpreter; for extension modules loaded dynamically from a shared library, it is the path name of the shared library file.
 This means you can't always rely on os.path.dirname(__file__) to find the folder of where your python file is located.  Here is a function that has four potential checks to get the python file's folder location:

import os
def getPythonFileLocation():
    """  returns the location of where the python file is located """
    if os.path.dirname(__file__) != "":
        return os.path.dirname(__file__)
    elif os.path.dirname(os.path.abspath(__file__)) != "":
        return os.path.dirname(os.path.abspath(__file__))
    elif os.path.dirname(os.getcwd()) != "":
        return os.path.dirname(os.getcwd())
        from inspect import getsourcefile
        return os.path.dirname(os.path.abspath(getsourcefile(lambda _:None)))

The function first tries the __file__ property using the os.path.dirname() then it tries another flavor of __file__ that I found from good old stack exchange. The 3rd check uses the os.getcwd() and finally it falls back on the inspect library.

Hopefully this will help prevent 'NoneType' issues when trying to join string paths.


Monday, June 16, 2014

Validating a File GeoDatabase Function

I recently created a bunch of data loading scripts that load data from some URL and copy it down local.  Nothing too special, but I noticed and interesting issue.  The file geodatabase (fgdb) would sometime randomly get corrupted and instead of the ArcGIS software seeing the fgdb as a database, it would see it as a folder in the ArcGIS software.  I create a little function to check the fgdb using the arcpy.Describe() to check the workspace ID and if it was a folder instead of a fgdb, I would erase and recreate the corrupted fgdb.  This seems to resolve the issue.
import os
import arcpy
from arcpy import env
def validate_fgdb(fgdb=env.scratchGDB):
       Checks to see if the FGDB isn't corrupt.  If
       the FGDB is corrupt, it then erases the database
       and replaces it with a new FGDB of the same name.
          fgdb - string - full path of the file geodatabase
        fgdb = str(fgdb)
        if os.path.isdir(fgdb) and \
            print 'workspace possible fgdb'
            desc = arcpy.Describe(fgdb)
            if hasattr(desc, "workspaceFactoryProgID") and \
               desc.workspaceFactoryProgID != "esriDataSourcesGDB.FileGDBWorkspaceFactory.1":
                shutil.rmtree(fgdb, ignore_errors=True)
                return True
            elif hasattr(desc, "workspaceFactoryProgID") and \
                 desc.workspaceFactoryProgID == "esriDataSourcesGDB.FileGDBWorkspaceFactory.1":
                return True
                return False

        elif os.path.isdir(fgdb) == False and \
            return True
            return False

Basically all it does is take a path to anything and sees if it 1 exists, 2, if it is a fgdb. I did add some additional benefits. If the path ends in ".fgdb" but does not exists, it will create the fgdb.

I have a bunch of theories on why the fgdb gets corrupted, but the leading offender is erasing tables from the fgdb causes something to get hosed in the database.  Table overwrites tend to cause this issue to happen as well.  .

Anyway enjoy and hopefully you can not eliminate this issue with your scheduled tasks or services.