Using LIKE in a For Loop with UpdateCursor

Question

I have a classified raster with a class value that is a very long concatenated string name (Class_Name below). I'm trying to use arcpy to generate integer labels ranging from 1-24 (which are the third concatenated sub-group in these long strings). Here's an example of a previous (manually manipulated) similar raster attribute table.

So far I've been manually using search criteria in ERDAS to find classes belonging to the same group such as:

$"Class_Names" contains "-14.01-" or $"Class_Names" contains "-14.02-" or $"Class_Names" contains "-14.03-"

I've tried using the following code (as a trial for the first two classes) with LIKE in a for loop with UpdateCursor, but I get a syntax error for my LIKE statement.

in_table = 'l12wm_agsup02.img'
field_names = ['Class_Name', 'crop']
with arcpy.da.UpdateCursor(in_table, field_names) as cursor:
    for row in cursor:
        if row[0] 'LIKE \'1.%\'':
            row[1] = 1
        elif row[0] 'LIKE \'2.%\'':
            row[1] = 2
        cursor.updateRow(row)

I've looked at Using LIKE clause in update cursor gives syntax error? and https://community.esri.com/thread/87848 but can't figure out how to use LIKE in the if else statements instead as a where clause in UpdateCursor.

I'm using ArcMap 10.5, Python 2.7

Answer 1

I would isolate the class you are after rather than searching for it. Then, simply assign row[1] that isolated value. For example:

in_table = 'l12wm_agsup02.img'
field_names = ['Class_Name', 'crop']
with arcpy.da.UpdateCursor(in_table, field_names) as cursor:
    for row in cursor:
        row[1] = row[0].split("-")[2].split(".")[0]
        cursor.updateRow(row)

Answer 2

This does not have to be done in a python script, it can be done simpler by using the calculate field tool as shown below:

If you want to run this as python the code would be:

arcpy.CalculateField_management("myRaster","crop","cropnumber( !class! )","PYTHON_9.3","""def cropnumber(s):/n  if s.find("-1.") != -1:/n    return 1/n  elif s.find("-2.") != -1 :/n    return 2/n  else:/n    return -999""")

Answer 3

You can use the in operator, for example:

with arcpy.da.UpdateCursor(in_table, field_names) as cursor:
    for row in cursor:
        if '1.' in row[0]:
            row[1] = 1
...

And instead of writing 24 if statements you can use a dictionary:

d = {'1.':1, '2.':2, '3.':3} #add all values here

with arcpy.da.UpdateCursor(in_table, field_names) as cursor:
    for row in cursor:
        for key in d:
            if key in row[0]:
                row[1]=d[row[0]]
                cursor.updateRow(row)

But this wont work since '2.' is in both '12.' and '22.' so you can do:

row[1] = row[0].split('-')[2].split('.')[0]

Answer 4

You can parse your text based on dash (-) to split the text and select the 3rd number to convert it to integer. Try the following python code in your field calculator:

def select(f):
    if f == ' ':
        return 0
    else:
        txt = f.split("-")[2]
        digit = int(round(float(txt),0))
        return digit

The above code assumes all the column of Class_Name is filled with information with the same structure. If the field is empty of text, it will return zero (0). However, I used round() function to round the class to the nearest whole number in case you have something like 4.98, it will return 5 instead of 4. But, if you want to truncate the digit numbers, you can simply change the line:

digit = int(round(float(txt),0))

to:

digit = int(float(txt))

Here is sample output: