I'm trying to calculate a field in Model Builder using the Calculate Field tool. I'm using the following code block and expression in the calculation, but am getting an "invalid syntax (, line 1)" error.

# Code Block:
def get_block(block_id):
    block_only = str(block_id)[1:]
    if block_only[-1].isalpha():
        return block_only.zfill(3)
        return block_only.zfill(2)

# Expression:

%block_id% is an in-line substitution that points to a string variable I create as the output of a custom Python script tool. Any ideas what the error is?


1 Answer 1


You need to quote the in-line substitution to pass the string variable.

The expression should read:




See the caution note in this help topic: http://resources.arcgis.com/en/help/main/10.1/index.html#//004000000004000000

  • Ah, yes, that must be it. Will verify tomorrow when I'm back at work. Thanks!
    – nmpeterson
    Mar 11, 2013 at 22:35
  • Just made the change and it worked perfectly. Thank you, again.
    – nmpeterson
    Mar 12, 2013 at 13:44

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