Is Python's calendar.month_name implementation of an empty string in the first index good practice or poor design?

Question

The documentation states:

An array that represents the months of the year in the current locale. This follows normal convention of January being month number 1, so it has a length of 13 and month_name[0] is the empty string.

Is this level of skeuomorphism warranted? Or is it confusing and potentially bug prone to start an array of expected values with no value?

Answer 1

It's better (and less confusing) to have the empty [0] placeholder at the beginning of the array so that you can just plug the month directly into the array indexer, than it is to start January at month 0 and have to perform a bit of conversion math to get the correct array index each time.

Sensible date implementations should not allow a month zero. Note that, for historical reasons, arrays typically start at an array index of zero.

• jonrsharpe: Should it be '' rather than None, though? The latter would cause noticeable trouble more quickly if something did end up accessing month_name[0].
• Robert Harvey: You can put whatever you want there.
• Adam Ashwal: Why not overload the [] function such that month_name[0] throws an error?
• Robert Harvey: That's probably a good idea.