Useful Exceptions

ZeroDivisionError

This appears when you try to force Python to perform any operation which provokes division in which the divider is zero, or is indistinguishable from zero. Note that there is more than one Python operator which may cause this exception to raise. Can you guess them all?

Yes, they are: /, //, and %.

ValueError

Expect this exception when you're dealing with values which may be inappropriately used in some context. In general, this exception is raised when a function (like int() or float()) receives an argument of a proper type, but its value is unacceptable.

TypeError

This exception shows up when you try to apply a data whose type cannot be accepted in the current context. Look at the example:

short_list = [1]
one_value = short_list[0.5]

You're not allowed to use a float value as a list index (the same rule applies to tuples, too). TypeError is an adequate name to describe the problem, and an adequate exception to raise.

AttributeError

This exception arrives – among other occasions – when you try to activate a method which doesn't exist in an item you're dealing with. For example:

short_list = [1]
short_list.append(2)
short_list.depend(3)

The third line of our example attempts to make use of a method which isn’t contained in the lists. This is the place where AttributeError is raised.

SyntaxError

This exception is raised when the control reaches a line of code which violates Python's grammar. It may sound strange, but some errors of this kind cannot be identified without first running the code. This kind of behavior is typical of interpreted languages – the interpreter always works in a hurry and has no time to scan the whole source code. It is content with checking the code which is currently being run. An example of such a category of issues will be presented very soon.

It's a bad idea to handle this exception in your programs. You should produce code that is free of syntax errors, instead of masking the faults you’ve caused.