def filter_chars_and_normalize():
    global data
    for i in range(len(data)):
        if not data[i].isalnum():
            data[i] = ' '
        else:
            data[i] = data[i].lower()
Replaces all nonalphanumeric chars in data with white space
dataset/ETHPy150Open crista/exercises-in-programming-style/04-cookbook/tf-04.py/filter_chars_and_normalize