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Conditional Calculate Field in Python

CoyPotts1

I have a script that works, but I replicate it in order to conditionally update 5 different fields. I would like to bolster the script to conditionally calculate all 5 fields into one if I can.

# Calculate Region

# Set local variables
inTable = nodeFeatures
inField = "Region1"
expression = "Reclass (!NodeID1!, !Region1!)"
codeBlock = """def Reclass (NodeID1, Region1):
    if NodeID1 != None:
        return region    #variable is declared earlier in the script
    else:
        return None"""

# Execute CalculateField
arcpy.CalculateField_management(inTable, inField, expression, "PYTHON_9.3", codeBlock)

The script above works just fine, but as I mentioned, I end up duplicating it to calculate 4 other fields. In this example we'll call all 5 fields Region1, Region2, etc... They would all have an accompanying NodeID1, NodeID2, etc...

Is it possible to expand upon this script in order to reduce the 5 separate scripts to calculate them all in one, or is it just the way it has to be in order to calculate a value of completely separate fields?

Thanks in advance!

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CoyPotts1

This may be getting me in the right direction.

The feature class that I am using has duplicate fields for each customer, so say each customer has the same 20 fields, and the only difference between them is their customer identification.

I want to loop through and say something like the following:

if Customer1NodeID != None:
     return regionvariable
if Customer2NodeID != None:
     return regionvariable
if Customer3NodeID != None:
     return regionvariable
else:
     return None

I'm just not sure how to nest multiple fields to be updated into one loop. Essentially I have 5 customers that I want to add data to their respective fields, but only if their NodeID field has data in it, otherwise leave it blank.

DarrenWiens2

Do you mean you want to loop through names, rather than numbers? If so, you can iterate through a list:

>>> list = ['Bob','Dave','Henry']
... for name in list:
...    print name
Bob
Dave
Henry

...or a dictionary:

>>> dict = {1:'a', 2:'b', 3:'c'}
... for item in dict:
...     print item
...     print dict[item]
...     
1
a
2
b
3
c

...or a tuple:

>>> tuple = (1, 2, 3)
... for item in tuple:
...     print item
...     
1
2
3

You can loop through unexpected things, too:

>>> string = "Hello"
... for letter in string:
...     print letter
...     
H
e
l
l
o

CoyPotts1

Actually, I made an oversight when I pasted my code. I omitted some of the verbiage to not include customer names and whatnot, so instead of each NodeID field literally having a number after it, each number actually represents a customer name.

But I will still use your sample code as reference for a FOR statement! .

Can you think of a way to do it without the FOR iteration?

CoyPotts1

This looks like it'll do just what I need. I'll give it a try a little later and respond with my results. Thanks for responding.

CoyPotts1

Wow, that's some pretty cool stuff! Thanks for sharing.

DarrenWiens2

You can place everything in a loop, counting from 1 - 5. Then, it's a matter of substituting the value into your expressions. This is untested, and I almost promise I got something wrong, but it should be a start:

# Calculate Region  

for i in range(1,6):  
    # Set local variables  
    inTable = nodeFeatures  
    inField = "Region" + i  
    expression = "Reclass (!NodeID" + i +"!, !Region" + i + "!)"  
    codeBlock = """def Reclass (NodeID" + i + ", Region" + i + "): 
        if NodeID" + i + "!= None: 
            return region    #variable is declared earlier in the script 
        else: 
            return None"""  
  
    # Execute CalculateField  
    arcpy.CalculateField_management(inTable, inField, expression, "PYTHON_9.3", codeBlock)

WesMiller

See Richard Fairhurst's blog Turbo Charging Data Manipulation with Python Cursors and Dictionaries

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