Python expression failing to execute

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07-07-2019 11:08 AM
MalcolmLittle
New Contributor III

Hello,

I'm trying to process a Python If statement using Field Calculator. What I want is to calculate the value of a string field by evaluating the values recorded in a double field. Essentially, calculating travel mode based on speed ranges (0 = stationary, 1-6 = walk, 7-19 = cycling, 20+ = driving).

However, my expression fails to process in ArcPro. Below is the expression in full, along with the output I received:

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Accepted Solutions
LanceCole
MVP Regular Contributor

Malcolm Little

First is you are getting a lock acquisition error, do you have multiple copies open of the table you are attempting to update?

Second use something like TravelMode = speedType (!Speed!) .  "Type" is a function in Python and should not be used as a def name.  It will work, but is poor practice.

Third for the Code Block, the way you have it coded "sp" is not assigned a value you have assigned the speed to "modey" when you called your function.  "sp" is only defined as a global and never set.  Your logic also does not handle NULL values or negative values that could be in your data.

def speedType(sp):
  if sp == 0:
    return "stationary"
  elif 1 <= sp <=6:
    return "walk"
  elif 7 <= sp <= 19:
    return "cycle"
  else:
    return "drive"
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3 Replies
LanceCole
MVP Regular Contributor

Malcolm Little

First is you are getting a lock acquisition error, do you have multiple copies open of the table you are attempting to update?

Second use something like TravelMode = speedType (!Speed!) .  "Type" is a function in Python and should not be used as a def name.  It will work, but is poor practice.

Third for the Code Block, the way you have it coded "sp" is not assigned a value you have assigned the speed to "modey" when you called your function.  "sp" is only defined as a global and never set.  Your logic also does not handle NULL values or negative values that could be in your data.

def speedType(sp):
  if sp == 0:
    return "stationary"
  elif 1 <= sp <=6:
    return "walk"
  elif 7 <= sp <= 19:
    return "cycle"
  else:
    return "drive"
‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍
DanPatterson_Retired
MVP Esteemed Contributor

check your conditions … if sp = 5 it should be in the range 1-6

sp = 5.
1 < sp <= 6  # ---- good
True

1 < sp >= 6  # ---- not correct
False
LanceCole
MVP Regular Contributor

Dan, 

Thanks for that catch.  I was looking at the code and not the logic in my responce.  Adjusted my reply as well...

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