We can use the chain() function to combine a collection of iterators into a single, overall iterator. This can be helpful to combine data that was decomposed via the groupby() function. We can use this to process a number of collections as if they were a single collection.
In particular, we can combine the chain() function with the contextlib.ExitStack() method to process a collection of files as a single iterable sequence of values. We can do something such as this:
from contextlib import ExitStackimport csvdef row_iter_csv_tab(*filenames: str) -> Iterator[List[str]]: with ExitStack() as stack: files = [ stack.enter_context(cast(TextIO, open(name, 'r'))) for name in filenames ] # type: List[TextIO] readers ...
