from collections import Iterable

def flatten(items, ignore_types=(str, bytes)):
  for x in items:
    if isinstance(x, Iterable) and not isinstance(x, ignore_types):
      yield from flatten(x)
    else:
      yield x

items = [1, 2, [3, 4, [5, 6], 7], 8]
# Produces 1 2 3 4 5 6 7 8
for x in flatten(items):
  print(x)

> items = ['Dave', 'Paula', ['Thomas', 'Lewis']]
> for x in flatten(items):
...   print(x)
...
Dave
Paula
Thomas
Lewis
>

def flatten(items, ignore_types=(str, bytes)):
  for x in items:
    if isinstance(x, Iterable) and not isinstance(x, ignore_types):
      for i in flatten(x):
        yield i
    else:
      yield x