Can I quickly get the minimum length of the most inner sub-lists within a list in python?

Question

This shows how to get the minimum length of first-level inner lists.

How can I return 4 for this list b=[[1,0,1,2,1,1,1,3111111,[1,1,6,7]],[31,1,4,51,1,1,1],[1,1,6,7,8]] as [1,1,6,7] only has 4 elements.

I can run a for-loop to get it. But can it be simpler?

I mean "the length of the shortest list that is at the same depth as the deepest list".

Answer 1

v1, minimum length at any depth:

>>> b = [[1,0,1,2,1,1,1,3111111,[1,1,6,7]],[31,1,4,51,1,1,1],[1,1,6,7,8]]
>>> def lists_in(L):
...     for element in L:
...         if isinstance(element, list):
...             yield element
...             yield from lists_in(element)
...             
>>> min(lists_in(b), key=len)
[1, 1, 6, 7]
>>> len(min(lists_in(b), key=len))
4

---

v2, with new requirement "the length of the shortest list that is at the same depth as the deepest list":

>>> def depths_and_lengths(L, depth=0):
...     for element in L:
...         if isinstance(element, list):
...             yield (depth, len(element))
...             yield from depths_and_lengths(element, depth-1)
...             
...             
>>> min(depths_and_lengths(b))[1]
4
>>> min(depths_and_lengths([[[1, 2]]]))[1]    # Stefan Pochmann example
2