Question

When programming in C# I usually write following arguments validation code:

void Process(object item) {
    if (item == null) throw ArgumentNullException();
    // code
}

Is it ‘Pythonic’ to do similar validation in Python? I really don’t want anybody pass None to Process method. What type of Python Exception should I use? (There are no standard ArgError or something like this)

def Process(item):
  if item == None: raise ArgNoneError('item')
  # code

Thanks

Answer 1

Usually, you’d just try to make do with the arguments you got — if someone passes None to your function it will fail anyway. There is no need to add complexity to your code without any benefit. Quite the contrary — often such tests prevent your code from working for cases it would work fine wwithout the tests.

If you want to raise some error anyway, use TypeError — it is meant for this purpose.