I have genomic data, and depending on the value of `ref` (it can either equal `'b37'` or `'hg19'`), the command I use will either have a `chr` at the beginning or have nothing at the beginning (e.g. `chr2` vs. `2`). 

Right now, I'm doing it like this: `min('chr', ref).strip('b37') + <chromosome_number>`.

This way is rather... creative, I'd say, and it wouldn't work if the name of the variables and such didn't work out as it did. I wonder if there is a more straightforward way to do this that still reserves the condense, "pythonic" form of my way.