Weeknotes for the week finishing Friday, 23rd May 2025.

Katie showed me a code snippet within which I noticed the following idiom:

del a_list[:]

I was sure that [:] copied the list, but I wasn’t sure what del did to it. Deleted a copy of the list? Deleted the contents of a copy of the list? What happened to the list?

After experimenting in the Python shell, I realised that del and [:] deleted the contents of the list. In other words, they’re equivalent to the following:

a_list.clear()

I find the use of del and [:] confusing. If you slice a list, then you get a new list. But if you delete a slice of a list, then you don’t: the elements contained by the slice are deleted from the list.

When we describe code as “idiomatic”, we mean “a characteristic mode of expression” (Oxford Languages). In this case, however, I mean “a group of words established by usage as having a meaning not deducible from those of individual words” (Oxford Languages).

This week, I also finished writing a proposal for a feature that will touch several of our systems and processes; talked about the future of the OpenPathology project; and helped Alice update the case-control studies documentation.