Merging geodatabases using ArcPy?

Question

I have a python script that is suppose to merge geodatabases. I have about 10 geodatabses, some of which have feature classes that are not in the others, everything else has the same schema. When I run the script, I get the following error:

Traceback (most recent call last):
  File "C:\Users\kahn8050\Desktop\PythonScripts\mergegeodatabases.py", line 29, in <module>
    lyrs = list_layers(gdb)
  File "C:\Users\kahn8050\Desktop\PythonScripts\mergegeodatabases.py", line 18, in list_layers
    for ds in arcpy.ListDatasets():
TypeError: 'NoneType' object is not iterable

I'm not exactly how to change the script so that it ignores NoneType and just merges the files that are the same. I have attached the script below:

import arcpy
import os
import time

START = time.time()

#### SET THESE VARIABLES BEFORE USING ####
model_path = (r"C:\Users\kahn8050\Desktop\PythonScripts\TEST\NFHL_04_20161108.gdb") # path to target geodatabase - schema should match that of input geodatabase(s)
paths_to_load = r'["C:\\Users\\kahn8050\\Desktop\\PythonScripts\\TEST\NFHL_06_20161110.gdb"]' # list of (str) paths to input geodatabase(s)

def list_layers(gdb):
    """
        Creates a list of feature classes in current workspace with full paths
        (including path to parent geodatabase). Returns list of layers.
    """
    print("\nGenerating layer list...")
    lyrs = [] 
    for ds in arcpy.ListDatasets():
        for fc in arcpy.ListFeatureClasses(feature_dataset = ds):
            fullpath = os.path.join(gdb, ds, fc)
            lyrs.append(fullpath)
    return lyrs

if __name__ == "__main__":
    for gdb in paths_to_load:
        arcpy.env.workspace = gdb

        print("***Beginning processing for {0}***".format(gdb))
        lyrs = list_layers(gdb)

        for lyr in lyrs:
            fc = os.path.basename(lyr)
            ds = os.path.basename(os.path.dirname(lyr))
                # if no dataset (i.e., fc is in root of geodatabase) then
                # ds = empty string
            target = os.path.join(model_path, ds, fc)
                # if ds = '' then join correctly ignores

            try:
            # append lyr to model_path/<ds>/<fc>
                arcpy.Append_management(lyr, target)
                print("Appended: {0}".format(target))
                with open ("appended_layers.txt", "a") as txt:
                    txt.write("{0}\n".format(lyr))
            except arcpy.ExecuteError as e:
                if "000732" in e:
                    pass
                    # target does not contain this feature class name
                    # TODO copy entire source layer to target?
                else:
                    # log failed attempts to append (e.g., non-matching schemas)
                    with open ("append_errors.txt", "a") as txt:
                        txt.write("***Failed to append {0}\n\t{1}\n".format(lyr, e))
                print(e)
                pass

    END = time.time()
    print("***Processing complete: time elapsed = {0} seconds***".format(END-START))

Answer 1

You are missing a slash \ in your paths_to_load

paths_to_load = r'["C:\\Users\\kahn8050\\Desktop\\PythonScripts\\TEST\NFHL_06_20161110.gdb"]' # list of (str) paths to input geodatabase(s)
                                                                      ^

Also you have for ds in arcpy.ListDataSets(), but this won't loop through anything if you don't have any feature datasets. This will result in the error 'NoneType' object is not iterable as your list contents will be NULL

Try this:

def list_layers(gdb):
    """
        Creates a list of feature classes in current workspace with full paths
        (including path to parent geodatabase). Returns list of layers.
    """
    print("\nGenerating layer list...")
    lyrs = [] 

    datasets = arcpy.ListDatasets()
    if datasets:
        for ds in datasets:
            for fc in arcpy.ListFeatureClasses(feature_dataset = ds):
                fullpath = os.path.join(gdb, ds, fc)
                lyrs.append(fullpath)

    fcs = arcpy.ListFeatureClasses()
    if fcs:
        for fc in arcpy.ListFeatureClasses():
            fullpath = os.path.join(gdb, fc)
            lyrs.append(fullpath)
    return lyrs