global name is undefined

Question

I'm trying to execute zonal statistics but I'm experiencing an error like this:

C:\Python27\ArcGIS10.5\python.exe "D:/WWF - Sustainable Hydropower/FRA/Code/f1_zonal_stats.py"
Running against: 2.7.12 (v2.7.12:d33e0cf91556, Jun 27 2016, 15:19:22) [MSC v.1500 32 bit (Intel)]
Running python 32 bit
> v0.3 (dev_gg)
Starting at 20190219155051
Traceback (most recent call last):
 File "D:/WWF - Sustainable Hydropower/FRA/Code/f1_zonal_stats.py", line 179, in <module>
 zonal_statistics(*argv)
 File "D:/WWF - Sustainable Hydropower/FRA/Code/f1_zonal_stats.py", line 48, in zonal_statistics
 set_environment(workspace, fd.masked_layer)
NameError: global name 'fd' is not defined

This is my code:

import csv
import datetime
import os
import sys
import time
from collections import defaultdict

import arcpy
from arcpy.sa import *

def zonal_statistics(*argv):
"""
    Calculates the Zonal statistics usinf a raster grid ans a zone grid/vector and extracts the results to a feature class
    :param values_path: Path to the values grid
    :param zones_path: Path to the zone grid
    :param 'out_feature_class': Feature class as target to append data
    :param type of statistics. Can be 'sum', 'avg', 'min', or 'max'
    :return: adds statistics values to 'out_feature_class'
    """

print ("> v0.3 (dev_gg)")
# Jan 6, 2017:
    # Added newly created RDD_B1_URB and NLI_B1_URB
    # Limited Nightlights to Urban areas
    # Limited Roads to outside urban areas (correlation with urban)
    # Changed ABS to CON (Consumption)

# Calculates river reach zonal stats from a set of input layers as defined in 'csv_name'

""" The output layer is defined in the CSV file"""
    # Its here: C:	emp\FFR_Results\1_ZonalResults\ZonalResults.gdb\streams_results_ffr

start = time.clock()
    __location__ = os.path.realpath(os.path.join(os.getcwd(), os.path.dirname(__file__)))

TIMESTAMP = int(datetime.datetime.fromtimestamp(time.time()).strftime('%Y%m%d%H%M%S'))
print "Starting at %s" % (str(TIMESTAMP))

workspaceFolder = os.path.join(r"C:	emp\FFR_Results\1_ZonalResults", 'Temp')
    make_sure_path_exists(workspaceFolder)

workspace = createWorkspace(workspaceFolder, TIMESTAMP)

# Set environment
    # csv_name = r"E:\Dropbox\Projects\FFR\Code\ZonalGridTransfer\FFR_India_input.csv"
    csv_name = r"E:\Dropbox\Projects\FFR\Code\ZonalGridTransfer\FFR_input.csv"

set_environment(workspace, fd.masked_layer)

ArdiNur_Armanto · Answer

Thanks for your kindly help. I'm still confused about how "mask_layer" could be added as an attribute to fd string object. Can you help me to explain it?

Luke_Pinner · Answer

A global var can be defined anywhere at the module level, i.e. in the same script file as your function and not inside a function or class.  I recommend not using globals though.  Just define it inside your zonal function or pass it in as an argument.

def zonal_statistics(*argv):
    """
    Calculates the Zonal statistics etc...
    """
fd = "whatever fd is...?"

def zonal_statistics(fd, *argv):
    """
    Calculates the Zonal statistics etc...

"""

#etc...
fd = "whatever fd is...?"
zonal_statistics(fd, rest of, your, args)

ArdiNur_Armanto · Answer

Can you help me to write the code about how to define fd as a global variable? Which line do I have to define fd in my code as I've shown above? I'm sorry because I'm the beginner user of Python so I'm still learning the programming.