How to separate comma from word (tokenization)

Question

I have some problem with tokenization, the assignment is to separate a sentence into words.

This is what I have done at the moment.

def tokenize(s):

    d = []
    start = 0
    
    while start < len(s):
        while start < len(s) and s[start].isspace():
            start = start+1

        end = start
        while end < len(s) and not s[end].isspace():
            end = end+1

        d = d + [s[start:end]]
        start = end
            
    print(d)

Running the program:

>>> tokenize("He was walking, it was fun")
['He', 'was', 'walking,', 'it', 'was', 'fun']

This works fine, but the problem is as you can see that my program will include the comma in the word walking. I want to separate the comma (and other "symbols") as an individual "word".

Such as:

['He', 'was', 'walking', ',', 'it', 'was', 'fun']

How can I modify my code to fix this?

Thanks in advance!

Answer 1

Here's a possible suggestion for a modification which will work with your specific example but which will definitely fail with examples like "How are you?!":

def tokenize(s):

    d = []
    start = 0
    
    while start < len(s):
        while start < len(s) and s[start].isspace():
            start = start+1

        end = start
        while end < len(s) and not s[end].isspace():
            end = end+1

        if(s[end-1] in ["!", ",", ".", ";", ":"]):
            d = d + [s[start:(end-1)]]
            d = d + [s[end-1]]
        else:
            d = d + [s[start:end]]
        
        start = end


            
    print(d)

tokenize("He was walking, it was fun!")
# ['He', 'was', 'walking', ',', 'it', 'was', 'fun', '!']