Python not catching exception

Question

For some reason my code is not catching an exception when I throw it. I have

def trim_rad(rad):
    ...

    if not modrad.shape[0]:
        raise IndexError("Couldn't find main chunk")
    return modrad, thetas

Then later I call that function:

try:
    modrad, thetas = trim_rad(rad)
except IndexError("Couldn't find main chunk"):
    return 0

Yet I still get a traceback with that exception. What am I doing wrong?

Answer 1

Catch just the IndexError.

try:
    raise IndexError('abc')
except IndexError('abc'):
    print 'a'



Traceback (most recent call last):
  File "<pyshell#22>", line 2, in <module>
    raise IndexError('abc')
IndexError: abc

try:
    raise IndexError('abc')
except IndexError:
    print 'a'


a # Output

So, reduce your code to

try:
    modrad, thetas = trim_rad(rad)
except IndexError:
    return 0

If you want to catch the error message too, use the following syntax:

try:
    raise IndexError('abc')
except IndexError as err:
    print err


abc