Joining words together with a comma, and "and"

You can avoid adding commas to each string in the list by deferring the formatting to print time. Join all the items excluding the last on ', ', then use formatting to insert the joined string with the last item conjuncted by and:

listed.append(inputed)
...
print('{}, and {}'.format(', '.join(listed[:-1]), listed[-1]))

---

Demo:

>>> listed = ['a', 'b', 'c', 'd']
>>> print('{}, and {}'.format(', '.join(listed[:-1]), listed[-1]))
a, b, c, and d

The accepted answer is good, but it might be better to move this functionality into a separate function that takes a list, and also handle the edge cases of 0, 1, or 2 items in the list:

def oxfordcomma(listed):
    if len(listed) == 0:
        return ''
    if len(listed) == 1:
        return listed[0]
    if len(listed) == 2:
        return listed[0] + ' and ' + listed[1]
    return ', '.join(listed[:-1]) + ', and ' + listed[-1]

Test cases:

>>> oxfordcomma([])
''
>>> oxfordcomma(['apples'])
'apples'
>>> oxfordcomma(['apples', 'pears'])
'apples and pears'
>>> oxfordcomma(['apples', 'pears', 'grapes'])
'apples, pears, and grapes'

This will remove the comma from the last word.

listed[-1] = listed[-1][:-1]

The way it works is listed[-1] gets the last value from the list. We use = to assign this value to listed[-1][:-1], which is a slice of the last word from the list with everything before the last character.

Implemented as shown below:

def lister():
    listed = []
    while True:
        print('type what you want to be listed or type nothing to exit')
        inputted = input()
        if inputted == '':
            break
        else:
            listed.append(inputted+',')
    listed.insert(-1, 'and')
    listed[-1] = listed[-1][:-1]
    for i in listed:
        print(i, end=' ')
lister()