Calling local variable causes TypeError: cannot unpack non-iterable NoneType object

Hi I was please wondering if I could have some help to understand why my self defined function works and gives the output I'm after, but when I try and assign variables to it outside of the function (to call header and rows separately) I get:

header,rows = parse_tsv(path) TypeError: cannot unpack non-iterable NoneType object

This is my code:

def parse_tsv(path):
    with open(path) as infile:

        header = []
        for line in infile:
            line = line.strip()
            header.append(line.split("\t")) 
            header = header[0]
            break

        rows = []
        for line in infile:
            line = line.strip()
            rows.append(line.split("\t"))
            if not line:
                continue
        rows = [[int(x) if x.isdigit() else x for x in i] for i in rows]
        rows = rows[1:]

    return print('header','=',header,'\n''rows','=',rows)

header,rows = parse_tsv(path)

header

I don't understand why it will give me a functioning and correct output with parser_tsv(path), but header,rows won't work. I don't think it can split them, but I am unsure how to go about fixing this. Thank you for your time!