validation of words in a sentence

I am trying to set validation for given sentence (input). These are criteria

1. Word contains letters, hyphens and punctuation only (no digits)
2. Maximum number of hyphen is one per word. If present, hyphens must be placed between letters (“ab-ab” not “-ab” or “ab-“
3. Maximum number of punctuation mark is one as well. If present, punctuation mark must be placed at the end of the word (“ab!”, “ab,” not “a!b” “a!!b”)

sentence = “these are valid words” is expected as [True, True, True, True]

sentence = “!this 1-s b8d!” is expected as [False, False, False]

sentence = “mciheal mnefiodonvass? W-O-W” is expected as [True, True, False]

sentence = “it’s Minecraft, not Mine-Craft!!” is expected as [False, True, True, False]) however i got [‘False’, ‘False’, ‘False’, ‘False’]

I got first three correct however for last one i am not getting the correct answer. Also for first criterion which is word with letters only will return True, it works for first but does not in last example. Can you explain me why and how can I fix it?

for last example I got [‘False’, ‘False’, ‘False’, ‘False’]

import string

def valid_words_mask(sentence):

sentence_list = sentence.split()
punctuations = string.punctuation.replace("-","")
true_false_list = []
count_hyphen = 0
count_punctuations = 0
validity = False

for words in sentence_list:
    for characters in words:
        
        if characters.isalpha():
            validity = True
        
        elif characters == "-":
            
            validity = True
            
        elif characters in punctuations:
            count_punctuations += 1
            validity = True

        else:
            validity = False
        
        break
    
    count_hyphen = words.count("-")
    for characters in words:
        if characters in punctuations:
            count_punctuations += 1
                        
    if validity is True:
    
        if any(number.isdigit() for number in words):
            validity = False
    
        if count_hyphen > 1 or count_punctuations > 1:
            validity = False
    
        if words.startswith("-") or words.endswith("-"):
            validity = False
        
        if count_punctuations == 1:
            for not_last in range(len(words)-1):
                if words[not_last] in punctuations:
                    validity = False
                    
            if words[-1] in punctuations:
                validity = True
    
        
    if validity is False:
        true_false_list.append("False")
    elif validity is True:
        true_false_list.append("True")


return (true_false_list.count("True"), true_false_list)

Answer

Based on your constraints, I suggest you break your code into a function with only 1 purpose: to check a single word. You can use something like:

def is_valid(word):

    punctuations = string.punctuation
    
    # constraint 1
    if not all([d in punctuations or d.isalpha() for d in word]):
        return False
    

    # constraint 2
    if word.startswith("-") or word.endswith("-"):
        return False
    if word.count("-") > 1:
        return False
    if "-" in word:
        dash_i = word.find("-")
        if (not word[dash_i - 1].isalpha()) or (not word[dash_i + 1].isalpha()):
            return False

    # constraint 3
    punct = [d for d in word if d in punctuations]
    if len(punct) > 1:
        return False
    elif len(punct) == 1:
        punct_i = word.find(punct[0])
        if punct_i != len(word) - 1:
            return False
            
    # all ok
    return True

To apply to each word in your sentence (split by whitespace I guess), so:

import string
for word in "it's Minecraft, not Mine-Craft!!".split():
    print(is_valid(word))

prints

False
True
True
False