List of List into List

[nilamo]

Taking a nested data structure, with multiple levels, and turning it into a single level, is known as "flattening".  There's many ways to do it, recursion is (I think) the way that's normally suggested, that way it can handle a list within a sublist within the list.

Maybe like this?

>>> cities = ["Tokyo", "London", ["Paris", "Madrid"]]
>>> def flatten(items):
...   for item in items:
...     if isinstance(item, list):
...       yield from flatten(item)
...     else:
...       yield item
...
>>> list(flatten(cities))
['Tokyo', 'London', 'Paris', 'Madrid']