Question

For example, there’re two similar codes:

The first one is:

 for chrom in bins:
     for a_bin in bins[chrom]:
         for pos in a_bin:
             pos = pos+100

The second one is:

 for chrom in bins:
     for a_bin in bins[chrom]:
         for pos in a_bin:
             if chrom=="chr1":
                 pos = pos*100

I was wondering that whether there’s a way to refactor the loop so that I don’t need to repeat writing code with the same structure..

Anyone has ideas about this?

Answer 1

This can be achieved with a generator function.

def gen():
    for chrom in bins:
        for a_bin in bins[chrom]:
           for pos in a_bin:
               yield pos

You can iterate through the items generated by gen(), though there is no “list of item” that is built — rather, it is constructed on demand:

for pos in gen():
    pass # add loop code here

This also means that, if you exit the loop early, the gen() method will be aborted (with an exception). Take a look at corutines to understand how this is implemented.