FindLabel not Defined in ArcMap labeling with Python Parser?

I think there is a bug in their parser as I am not getting identical behavior between a Python prompt and the label expression evaluator.

Try the following as a workaround:

def FindLabel ( [Direction] ):
    return "{}° {}' {}".format(*[Direction].split('-')) + chr(34)

There were two problems:

Due to a bug with the ESRI parser (this is legal in pure Python), you cannot escape a double-quote with a backslash if the string is surrounded by double-quotes. Similarly, you cannot escape a single-quote with a backslash if the string is surrounded by single-quotes, although this is also legal in pure Python. Triple-quoted strings also don't work the same as at a Python prompt.

Examples that work in a Python prompt but not in a Python label expression:
- "I am 6'2\" tall."
- """I am 6'2" tall."""
- 'I am 6\'2" tall.'
- '''I am 6'2" tall.'''
To work around this, you can instead concatenate it or format it into the string separately.
The str.format() function expects args or kwargs, not a sequence. You can use the * operator to unpack a sequence into arguments, which is what I did above, and it works.

Side note -- because this is a 1-liner you can uncheck the "Advanced" box and just use the expression itself instead of a complete function:

"{}° {}' {}".format(*[Direction].split('-')) + chr(34)

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