I'm using the Field Calculator .replace function to replace WEST, EAST, NORTH, SOUTH to W, E, N and S and I'm using 4 scripts !PREDIR!.replace("WEST*","W") and so forth.

I would like to use one string to do this, how can I do this?

  • Should "WESTON" be replaced with "W"? It is unclear what values are to be expected in that field. In any event I think this question is much more Python than ArcPy and so should be researched at Stack Overflow.
    – PolyGeo
    Aug 14, 2017 at 19:15

4 Answers 4


You can try this:

Predir field has already North, South, East, West

  • good idea to shorten the code
    – atxgis
    Aug 14, 2017 at 17:10

Python allows you to string together functions. In your case, you can string together multiple .replace() functions into a single line of code in the field calculator.

!PREDIR!.replace('NORTH', 'N').replace('SOUTH', 'S').replace('EAST', 'E').replace('WEST', 'W').replace('west', 'W)

Use a dictionary:

ReplaceDict = { "WEST": "W",
                "EAST": "E",
                "NORTH": "N",
                "SOUTH": "S"}

for r in ReplaceDict:
    if !PREDIR! in r:

The closest thing to "one string" would be to use a regex:

import re
predir = re.sub(r'([NSEW])[OAE][UR]?[ST][TH]\*', r'\1', !PREDIR!) 

The question then becomes if it's better to have four readable lines, or one unreadable one that may have some gotchas (the above will shorten WORST* to W too!).

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