Functions, docstrings and a mistake by me at the end

In class today we spoke about group coursework a bit but mainly spent time looking at docstrings.

You can see a recording of this here: https://cardiff.cloud.panopto.eu/Panopto/Pages/Viewer.aspx?id=7c020a93-9855-44f2-9f30-b1050118b4a9

We spoke about the numpy docstring format, which is specified here: https://vknight.org/pfm/building-tools/02-functions-and-data-structures/how/main.html#how-to-write-a-docstring

I used the example of verifying the following identity to demonstrate this:

\[(a + b) ^ n = \sum_{i=0}^n\binom{n}{i} a ^ i b ^ {n - i}\]

You can find a notebook with all this here

I’m really sorry about how confusing the ending of class today must have been I made a mistake (my fault entirely).

The notebook linked to above does not contain the error.

When it came to fixing the floating point error I wrote:

sum(int(scipy.special.binom(n, i) * a ** i * b ** (n - i)) for i in range(n + 1))

But the mistake I made here (and again I apologise for the crash and burn at the end of the class) is that the closing bracket of int should have been after the binom and not after the entire calculation.

sum(int(scipy.special.binom(n, i)) * a ** i * b ** (n - i) for i in range(n + 1))

The difference is subtle but it is important as scipy.special.binom(n, i) will always be a float with 0 fractional part. So taking the int of it will give what we need.

I’ll happily go over this again on Tuesday if I can clarify things. The important thing to take from today is the approach and the docstrings.