Take the "Head" of every file in a directory?

Take the "Head" of every file in a directory?

I am working with large files, and my question here is two-fold.
1) Bash - For testing purposes, I would like to iterate over every file in
a given directory, taking the Head of each file (say Head 10000), and be
left with a cut-down version of each. Either in the same directory or
another it doesn't matter a whole lot, though I suppose the same would be
preferred.
2) Python3 - How can I do this programmatically? I imagine I need to use
the os module?