Mdthbs

Below is my code for the Comma Code problem from Chapter 4 of Automate the Boring Stuff with Python. Is there anything I can do to make it cleaner?

Comma Code

Say you have a list value like this:

spam = ['apples', 'bananas', 'tofu', 'cats']

Write a function that takes a list of values as an argument and returns a string with all the items separated by a comma and a space, with 'and' inserted before the last item. For example, passing the previous spam list to the function would return 'apples, bananas, tofu, and cats'. But your function should be able to work with any list passed to it.

The output of this program could look something like this:
apples, bananas, tofu, and cats

import sys



spam = ['apples', 'bananas', 'tofu', 'cats']



def print_list(list):

    for item in list:

        if len(list) == 1:

           print(list[0]) 

        elif item != list[-1]:

            print(item + ', ', end='')

        else:

            print('and ' + list[-1])





print_list(spam)

You've got an odd bug with your code.

Given the 8th menu item from the greasy spoon café:

spam = ["Spam", "Spam", "Spam", "egg", "Spam"]

You will get:

and Spam

and Spam

and Spam

egg, and Spam

since you are not testing whether you are at the last item in your list, but rather if the current item is the same as the last item in the list.

Testing for a length 1 list should not be done inside the loop of all items; it should be done exactly once, outside the loop. Ie (but still with the above bug):

if len(list) == 1:    # Test outside of loop

   print(list[0]) 

else:

    for item in list:

        if item != list[-1]:

            print(item + ', ', end='')

        else:

            print('and ' + list[-1])

Want you really want to do is print all but the last item in the list one way, and the last item a different way:

# If there are more than 1 items in the list...

if len(list) > 1:



    # Print all but the last item, with a comma & space after each

    for item in list[:-1]:

        print(item + ', ', end='')



    # with "and " printed at the very end, just before ...

    print("and ", end='')



# print the last (or only) item in the list.

print(list[-1])

although this still assumes at least one item in the list.

Alternately, you could join() all but the last item, and then add ", and " along with the final item.

msg = list[-1]

if len(list) > 1:

    msg = ", ".join(list[:-1]) + ", and " + msg

print(msg)

You are doing import sys, but not using sys anywhere. You can remove the import.

Unused import statement: that should be cleaned up.

import sys

Bad parameter name: def print_list(list): The keyword list() is a built-in function, you don't want your variable/parameter/function/method/class named like built-ins because later when you start relying on such keywords, this will create problems.

Example: (run this interactively)

>>> word = 'mouse'

>>> letters = list(word)

>>> letters

['m', 'o', 'u', 's', 'e']

>>> list = 5

>>> new_letters = list(word)

Troubles ...

Traceback (most recent call last):

File "<pyshell#3>", line 1, in <module>

list(word)

TypeError: 'int' object is not callable

I think the example is self-explanatory why you shouldn't use built-ins in your naming.

def print_list(list):

Docstrings: Python documentation strings (or docstrings) provide a convenient way of associating documentation with Python modules, functions, classes, and methods. ... A docstring is simply a multi-line string, that is not assigned to anything. It is specified in source code that is used to document a specific segment of code. You should include a docstring to your public functions indicating what they do and type hints if necessary.

This is a bit complicated

for item in list:

    if len(list) == 1:

       print(list[0]) 

    elif item != list[-1]:

        print(item + ', ', end='')

    else:

        print('and ' + list[-1])

The whole function can be simplified and written properly:

def separate(items: list):

    """Return a string of the words in items separated by a comma."""

    if len(items) > 1:

        return ', '.join(items[:-1]) + ', and ' + items[-1]

    if len(items) == 1:

        return items[0]

    if not items:

        raise ValueError('Empty list')

then use if __name__ == '__main__': guard at the end of your script which allows it to be imported by other modules without running the whole script.

if __name__ == '__main__':

    spam = ['apples', 'bananas', 'tofu', 'cats']

    print(separate(spam))