topic Re: how to use a variable as an object property in python in Python Questions

how to use a variable as an object property in python

lukestudden — Thu, 05 May 2011 15:52:56 GMT

Hi all,

I am using python (9.3) to automate the creation of numerous Featureclasses. Along the way I am adding a new column (field) to each which the field name is essentially a variable as it is all data driven. I am then using the UpdateCursor to update the value of the field with the value of another within the same Feature class. The problem is that since the field name I have added is a variable, I can not use the update cursor to refer to it as it changes after each loop iteration. Is there any way you can use a variable as an objects property, eg.

instead of explicitly stating the field to be updated eg. updaterow1.car1 I would like to use a variable eg: updaterow1.carnumber

Carnumber would then change after each iteration eg. car1, car2, car3 etc.

Is this possible?

Thanks!

Re: how to use a variable as an object property in python

LoganPugh — Thu, 05 May 2011 16:02:52 GMT

See Accessing Data Using Cursors. Particularly the setValue and getValue methods.

Re: how to use a variable as an object property in python

lukestudden — Thu, 05 May 2011 16:26:45 GMT

Hi Logan,

thanks for the reply. I am still struggling to see this. Could you shed any more light on this at all? I would be most grateful! Below is a simplified version of what I have;

Thanks

fieldname = "car "+ str(incrementingcounter)

updaterows1 = gp.updatecursor(outputpoly1)
updaterow1 = updaterows1.next()

    while updaterow1: # selects the entire row, but row has properties hence .fieldname

        #### i essentially need this to be something like updaterow1.fieldname
        updaterow1.count_0 = updaterow1.Join_Count

        updaterows1.updaterow(updaterow1)
        updaterow1 = updaterows1.next()

del updaterows1

Re: how to use a variable as an object property in python

LoganPugh — Thu, 05 May 2011 16:38:29 GMT

There are two basic ways to get and set field values on a row:

* Using the field name, as in value = row.road_type
* Using getValue and setValue, as in value = row.getValue("road_type")

Try using the getValue and setValue methods instead of using field names as properties.

Re: how to use a variable as an object property in python

lukestudden — Thu, 05 May 2011 20:29:29 GMT

Does that mean i can use:

Row.getvalue(fieldname)

As a direct replacement of what i am currently using?

Updaterow1.car1

Re: how to use a variable as an object property in python

LoganPugh — Thu, 05 May 2011 21:12:12 GMT

Yes, they work the same way except that they allow you to pass a variable for the field name instead of hardcoding it.