def find_most_frequent(text):

    import math

    dict_for_words_and_numbers_of_words = {}
    list_for_dict_values = []
    list_for_dict_keys = []

    text = text.lower()

    for i in text:
        if not str(i).isalpha() and i != ' ':
            text = text.replace(i, '')

    text = text.split()

    for word in text:
        if word in dict_for_words_and_numbers_of_words:
            dict_for_words_and_numbers_of_words[word] += 1
        else:
            dict_for_words_and_numbers_of_words[word] = 1

    for i in dict_for_words_and_numbers_of_words.values():
        list_for_dict_values.append(i)

    for i in dict_for_words_and_numbers_of_words.keys():
        list_for_dict_keys.append(i)

    kk = []
    for i in range((len(list_for_dict_values))):
        if list_for_dict_values[i] == max(list_for_dict_values):
            kk.append(list_for_dict_keys[i])

    return print(kk)

find_most_frequent('my name is andrew Is my best name')