topic Re: Counting items that go through your loop in Python Questions

Counting items that go through your loop

MatthewRusso — Fri, 10 Dec 2021 20:54:44 GMT

As I dive further into Python, I find myself making a "GIS Module" that calls functions that are useful to my work.

I created a quick find and replace function but i want to print off the total number items replaced.

I also have a show unique value function that lists all the unique items in a field and their values. I want to include just a simple line like:

547 items replaced

here are my 2 functions can anyone explain how to include this:

def field_counter(table,fieldname):
     values = [r[0] for r in arcpy.da.SearchCursor(table, [fieldname])]
     unique_values = set(values)
     count_dict = {}
     for value in unique_values:
          count_dict[value] = values.count(value)
          print("{0} Unique Value: {1} has {2} attribute(s)".format(fieldname, value, count_dict[value]))

def find_and_replace(table, field, find, replace):
     with arcpy.da.UpdateCursor(table, [field]) as cursor:
          for row in cursor:
               if row[0] == find:
               row[0] = replace
               cursor.updateRow(row)
               print(row[0] + ' was replaced by' + replace)
          elif row[0] != find:
               print(row[0] + ' was not replaced')

Re: Counting items that go through your loop

DarrenWiens2 — Fri, 10 Dec 2021 20:54:47 GMT

Untested, but should work like so:

counter = 0
with arcpy.da.UpdateCursor(table, [field]) as cursor:
 for row in cursor:
   if row[0] == find
     row[0] = replace
     cursor.updateRow(row)
     counter = counter + 1
print counter
return counter

To pass counter back to the calling function, you would 'return counter', but since we don't see where you call the function, it's hard to write it. It would be something like:

count = find_and_replace(table, field, find, replace)
print count # the number returned by function

Re: Counting items that go through your loop

MatthewRusso — Thu, 26 Feb 2015 18:33:38 GMT

I didn't realize that it was that easy.... haha. Here I was thinking I needed to do a bunch of stuff in the loop to make this work, Thanks!

Re: Counting items that go through your loop

TomSellsted — Fri, 10 Dec 2021 20:54:50 GMT

Matthew,

To do iterative counts I calculate the modulo of the desired increment. This can be useful when you have a large dataset and want to see its progress. It would look something like this:

counter = counter + 1
if (counter%1000) == 0:
    print str(counter)

Note that in order to print an integer you will need to make it a string too.

Regards,

Tom

Re: Counting items that go through your loop

DarrenWiens2 — Fri, 10 Dec 2021 20:54:53 GMT

Python will print integers just fine without casting it to string. The problem I think you are referring to arises when you try to concatenate strings with integers.

This works:

>>> for i in range(100):
...     count = count + 1
...     print count

This doesn't work:

>>> for i in range(100):
...     count = count + 1
...     print "Count: " + count

Re: Counting items that go through your loop

MatthewRusso — Thu, 26 Feb 2015 20:10:01 GMT

Good information. I still consider myself a Novice at this by I am trying to absorb as much as possible.

Thanks Darren Wiens‌ and Tom

Re: Counting items that go through your loop

TomSellsted — Thu, 26 Feb 2015 21:05:54 GMT

Darren,

You are correct sir.

counter = counter + 1

if (counter%1000) == 0:

print str(counter) + " items processed."

would be the correct syntax.

Regards,

Tom

Re: Counting items that go through your loop

BlakeTerhune — Fri, 10 Dec 2021 20:54:55 GMT

Might be better (cleaner) to use string format(). Based on the correct answer from Darren Wiens‌, this is what I would do.

counter = 0
with arcpy.da.UpdateCursor(table, [field]) as cursor:
    for row in cursor:
        if row[0] == find:
            row[0] = replace
            cursor.updateRow(row)
            counter += 1
print "{} items processed".format(count)
return counter