Selecting feature class with a specified name in Arcgis python (Arcpy)

Question

I am using arcpy and I want to extract a specific feature class called "building" nested in a number of geodatabase within my workspace.

Here is the code:

import arcpy
import os

workspace = "C:/Wiley/P1/gis"
search = "Building"
outdir = "C:/Wiley/P1/gis/HK80.gdb"
fc = []

walk = arcpy.da.Walk(workspace, datatype="FeatureClass", type="Polygon")

for dirpath, dirnames, filenames in walk:
          for filename in filenames:
             if search == filename:
                     fc.append(os.path.join(dirpath, filename))
if fc:
     output = os.path.join(outdir, os.path.basename(search) + "_merge")
     arcpy.Merge_management(fc, output)

This code was successful.

But there are many other featureclass in the geodatabase apart from "Building" So I expanded the code a bit and try to loop the merge command through all these feature class:

    import arcpy
import os

#--------------------------
#example list workspace
arcpy.env.workspace = "C:/Wiley/P1/gis/HKU_Job69.gdb"

#Generate exmaple list dataset
datasets = arcpy.ListDatasets(feature_type='All')
datasets = [''] + datasets if datasets is not None else []
fc_list = []

#--------------------------

#where all the gdb is nested
workspace = "C:/Wiley/P1/gis"

#define output
outdir = "C:/Wiley/P1/gis/HK80.gdb"

#List of Feature classes
fc = []

#define walk for looping
walk = arcpy.da.Walk(workspace, datatype="FeatureClass", type="Any")

for ds in datasets:
     for fc_example in arcpy.ListFeatureClasses(feature_dataset=ds):
        fc_list.append(fc_example)


for f in fc_list: #Loop through the list   
   for dirpath, dirnames, filenames in walk:        
        for filename in filenames:
           if f == filename:
                     fc.append(os.path.join(dirpath, filename))
   if fc:
        output = os.path.join(outdir, os.path.basename(search) + "_merge")
        arcpy.Merge_management(fc, output)

This is where I hit a wall. Is there anything wrong with this code? I am new to Python so for a trained eye you guys may spot out the error in the logic immediately. The f variable didn't seem to loop at all.

Answer 1

Try neatening up your indents - for example, you don't need to indent the first line where you import arcpy. Also, in your first script (the one that is working), the arcpy.Merge_management tool is not in a loop. In the second (not working) script, it's in the fc_list loop, and if I understand your script's logic correctly, it doesn't need to be.

You can also try adding a print statement within the fc_list loop to see if it's running at all - like this:

for f in fc_list: #Loop through the list   
    for dirpath, dirnames, filenames in walk:        
        for filename in filenames:
            print filename
            if f == filename:
                fc.append(os.path.join(dirpath, filename))
                print 'appended'
            else:
                print 'nope!'
    print 'done with walk'

if fc:
    output = os.path.join(outdir, os.path.basename(search) + "_merge")
    arcpy.Merge_management(fc, output)