Cambridge practical task: text records, hashing and evidence

"""Original text-loaded hash-table simulation; not binary-file access."""
from pathlib import Path

def insert(table, identifier, name):
    for offset in range(len(table)):
        index = (identifier % len(table) + offset) % len(table)
        if table[index] is None or table[index][0] == identifier:
            table[index] = (identifier, name)
            return index
    raise OverflowError('table full')

def find_record(table, identifier):
    for offset in range(len(table)):
        index = (identifier % len(table) + offset) % len(table)
        if table[index] is None:
            return None
        if table[index][0] == identifier:
            return table[index]
    return None

def load_records(text, capacity=5):
    if type(capacity) is not int or capacity < 1:
        raise ValueError('positive integer capacity required')
    table, rejected = [None] * capacity, []
    for line_number, raw in enumerate(text.splitlines(),1):
        if not raw.strip():
            continue
        fields = raw.strip().split(',')
        if len(fields) != 2 or not fields[0].isascii() or not fields[0].isdigit() or not fields[1].strip():
            rejected.append((line_number,'format'))
            continue
        try:
            insert(table,int(fields[0]),fields[1].strip())
        except OverflowError:
            rejected.append((line_number,'full'))
    return table,rejected

def save_records(table):
    return ''.join(f'{row[0]},{row[1]}\n' for row in table if row is not None)

if __name__ == '__main__':
    try:
        table,rejected = load_records(Path('records.txt').read_text(encoding='utf-8'))
        print(list(enumerate(table)))
        print('Lookup 17:',find_record(table,17))
        print('Rejected:',rejected)
        Path('saved-records.txt').write_text(save_records(table),encoding='utf-8')
    except (OSError,UnicodeError) as error:
        print(f'Cannot read/write task files: {error}')