<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def read_csv(directory):
    '''
    Scrape a twitter archive csv, yielding tweet text.

    Args:
        directory (str): CSV file or (directory containing tweets.csv).
        field (str): Field with the tweet's text (default: text).
        fieldnames (list): The column names for a csv with no header. Must contain <field>.
                            Leave as None to read CSV header (default: None).

    Returns:
        generator
    '''
    if path.isdir(directory):
        csvfile = path.join(directory, 'tweets.csv')
    else:
        csvfile = directory

    with open(csvfile, 'r') as f:
        for tweet in csv.DictReader(f):
            try:
                tweet['text'] = tweet['text'].decode('utf-8')
            except AttributeError:
                pass

            yield tweet