How to get minimum length of a sublist from dictionary except zero? [closed]

Given a dictionary with list values, how can I get the number of elements where the value has a specific minimum length?

Below is my attempt:

mm = {1: [2, 5],
      2: [3, 4, 7], 
      3: [1, 4], 
      4: [], 
      5: [1], 
      6: [3, 4]}

item = min(mm, key=lambda f: len(mm[f]))

Expected output: 5

Just filter out the empty elements and pass the result to min:

item = min((key for key, value in mm.items() if value), key=lambda k: len(mm[k]))

The inner genexpr filters to only those keys where the value is truthy (non-empty), and min then operates only on those keys known to have non-empty values.

If you want the value itself, not the key that refers to it, this is even simpler:

min_non_empty_value = min(filter(None, mm.values()), key=len)

filter(None is an optimized case for discarding falsy values (empty lists in this case), and by removing the need to deal with/return a key, you can just use key=len directly to check the length of each value.