topic Re: Calculating counting field in Python Questions

Calculating counting field

KelvinMwakomo — Wed, 08 Mar 2017 06:02:20 GMT

Hello guys,

Assistance please,

I have a table below;

From there i created a new field "code" so i want to calculate a sequential numbers based on how much the "Unique_no" appears like the one below;

Regards,

Kelvin.

Re: Calculating counting field

NeilAyres — Sat, 11 Dec 2021 13:13:11 GMT

You could do this with an update cursor and a dictionary, something like this...

data_dict = {}
with arcpy.da.UpdateCursor(fcName, ["Unique_no", "Code"]) as Cur:
    for row in Cur:
        if row[0] in data_dict:
            # increment counter
            data_dict[row[0]] += 1
        else:
            data_dict[row[0]] = 1
        # update code
        cnt = dat_dict[row[0]]
        row[1] = cnt
        Cur.updateRow(row)
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Re: Calculating counting field

KelvinMwakomo — Wed, 08 Mar 2017 07:21:14 GMT

Thanks Neil,

See if I'm wrong somewhere because i am not good in python.

Re: Calculating counting field

NeilAyres — Wed, 08 Mar 2017 07:28:06 GMT

Firstly try and run this as a script in IDLE or pyscripter or something.

You have the indentation wrong. The line starting else:

Should be at the same level as the if:

Indentation in python is a crucial part of the language syntax.

Try doing a bit of reading up on python first.

Re: Calculating counting field

NeilAyres — Wed, 08 Mar 2017 07:29:18 GMT

And the last 3 lines also at the same indentation level as the if:

Re: Calculating counting field

JoshuaBixby — Sat, 11 Dec 2021 13:13:14 GMT

Using defaultdict allows the code to be simplified/condense a bit:

from collections import defaultdict

data_dict = defaultdict(int)
with arcpy.da.UpdateCursor(fcName, ["Unique_no", "Code"]) as cur:
    for uniq, code in cur:
        data_dict[uniq] += 1
        cur.updateRow([uniq, data_dict[uniq]])‍‍‍‍‍‍‍‍‍‍‍‍‍