Clean Code in Python

Creating sequences

Maybe our object does not define the __iter__() method, but we still want to be able to iterate over it. If __iter__ is not defined on the object, the iter() function will look for the presence of __getitem__, and if this is not found, it will raise TypeError.

A sequence is an object that implements __len__ and __getitem__ and expects to be able to get the elements it contains, one at a time, in order, starting at zero as the first index. This means that you should be careful in the logic so that you correctly implement __getitem__ to expect this type of index, or the iteration will not work.

The example from the previous section had the advantage that it uses less memory. This means that is only holding one date at a time, ...