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Trying to return everything except the last element in a field after splitting it. Using ArcMap 10.2.2 in the field calculator. 

!ST_NAME!.split(" ")[:-1]

This returns a null value in attribute table. If a I use the same approach in python interactive window it seems to work:

a = "Johnny be good"

>>> b = a.split(" ")[0:-1]
>>> b
['Johnny', 'be']
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  • 5
    The return value is a list, which is not compatible to the field, which is rejected by the parser hence the null value. To use this in a field calculation for a string field you need to 'join' it " ".join(!ST_NAME!.split(" ")[:-1]) to make it into a string.
    – Michael Stimson
    Commented Apr 25, 2016 at 22:11
  • Another approach you can use would be to find the rightmost space and then slice into the string with that index. f = "101 first street"; f[:f.rfind(" ")]
    – Paul
    Commented Apr 25, 2016 at 23:22

1 Answer 1

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Expanding on my previous comment...

The problem with your statement is that the returned value from string.split is a list and the field you're trying to calculate into is a string, these types are incompatible so the parser ignores the value and sets the string to null.

To turn a list into a string you need to use join:

>>> a = "Johnny be good"
>>> b = a.split(" ")[0:-1]
>>> print b
['Johnny', 'be']
>>> c = " ".join(b)
>>> print c
Johnny be
>>>

b is a list object, c is a string... So to field calculate everything but the last word in a string into a string field use:

" ".join(!ST_NAME!.split(" ")[:-1])
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