How to know which line gives error in python?

Question

I am new to Python so please excuse my rudimentary question. When I get an error I can usually figure out what line caused the error, but sometimes from the error message itself I can't decide which line is responsible. So I add some messages between the lines to track the issue. Is there any more effective solution to that? I am running my codes form ArcGIS toolbox script and I am not sure if I can trace the errors from there.

Answer 1

I always use print statements (okay, function in Py3). It's the most standard way. Just use it to track where are you now in your program, and what are you doing.

However, if your application processes a large data, or if it's a large application, print statements may be not enough. Sometimes, you'll need try and except statements, just to narrow the search of the error.

More on error handling? Here !

This may also be useful.

Answer 2

If youre trying to do this with a excepted error do this:

import traceback
import sys

try:
    raise Exception("foo")
except:
    for frame in traceback.extract_tb(sys.exc_info()[2]):
        fname,lineno,fn,text = frame
        print "Error in %s on line %d" % (fname, lineno)

otherwise just read the traceback