glob_wildcards foo

[ctb]

Anneliek ter Horst
Hello!
I have a question regarding input files.
When defining input files at the top of a Snakefile, like this:
SAMPLES, = glob_wildcards('/group/ctbrowngrp2/scratch/annie/2023-sourmash-viruses/{ident}.fa
Why is the , needed after SAMPLES?
11:14 AM
titus
💬 glob_wildcards returns an object that (among other things) can be unpacked via iteration. The SAMPLES, says “please unpack this via iteration; I expect one element only.”

11:14 AM
it is equivalent to
SAMPLES = list(glob_wildcards(...))[0]
with the added bonus that if there is more than one element in the list, Python complains.
11:16 AM
The object itself is pretty cool. You could also do
wc_obj = glob_wildcards(...)
SAMPLES = wc_obj.ident
as a way of pulling out just the matches to ident . If you had multiple wildcards being learned by glob_wildcards, this would be a good way to access them.