file=open('pověst.txt','r')
kniha=file.read()
def tokenize():
    if kniha is not None:
        slova = kniha.lower().split()
        return slova
    else:
        return None

def count_slova(tokens, token):
    počet = 0

    for prvek in tokens:

        word = prvek.replace(",","")
        word = word.replace(".","")

        if word == token:
            počet += 1
    return počet



slova=tokenize()

word='a'
frequency=count_slova(slova, word)
print('Frekvence slova "' + word + '" je: ' + str(frequency))
input('Press ENTER to exit')