Condition checking vs. Exception handling
- by Aidas Bendoraitis
When is exception handling more preferable than condition checking? There are many situations where I can choose using one or the other.
For example, this is a summing function which uses a custom exception:
# module mylibrary
class WrongSummand(Exception):
pass
def sum_(a, b):
""" returns the sum of two summands of the same type """
if type(a) != type(b):
raise WrongSummand("given arguments are not of the same type")
return a + b
# module application using mylibrary
from mylibrary import sum_, WrongSummand
try:
print sum_("A", 5)
except WrongSummand:
print "wrong arguments"
And this is the same function, which avoids using exceptions
# module mylibrary
def sum_(a, b):
""" returns the sum of two summands if they are both of the same type """
if type(a) == type(b):
return a + b
# module application using mylibrary
from mylibrary import sum_
c = sum_("A", 5)
if c is not None:
print c
else:
print "wrong arguments"
I think that using conditions is always more readable and manageable. Or am I wrong? What are the proper cases for defining APIs which raise exceptions and why?
