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Python The Solution: For Loops

Posted by amandae
amandae
15,727 Points

How to add an "and" before the last item of a joined list for readability?

I'm working on the list of school year birthdays in the "For Loops" practice session.
I'm curious, just for nice end-point formatting, how does one join a list with correct grammar.

Right now, I end up with:

Shawna, Amaya, Kamal, Xan have school year birthdays.
James, Sam have birthdays in the summer.

I would like it to say:

Shawna, Amaya, Kamal, and Xan have school year birthdays.
James and Sam have birthdays in the summer. (This would be easy if I knew ahead there were only two, but we don't know the number to start.)

Here's the code I have so far.

BIRTHDAYS = (
    ("James", "9/8", True, 9),
    ("Shawna", "12/6", True, 22),
    ("Amaya", "28/2", False, 8),
    ("Kamal", "29/4", True, 19),
    ("Sam", "16/7", False, 22),
    ("Xan", "14/3", False, 34),
)

sybdays = []
nsybdays = []

for e in BIRTHDAYS:
    bday = e[1].split('/')
    if int(bday[1]) <= 6 or int(bday[1]) >= 9:
        sybdays.append(e[0])
    else:
        nsybdays.append(e[0])
print(f'{", ".join(sybdays)} have school year birthdays.')
print(f'{", ".join(nsybdays)} have birthdays in the summer.')

Thanks!

1 Answer

jb30
jb30
44,805 Points

I don't know if there is a built-in method for that. If you don't care about the serial comma and you know that there are at least two elements in each list, you could try

print(f'{", ".join(sybdays[:-1]) + " and " + sybdays[-1]} have school year birthdays.')
print(f'{", ".join(nsybdays[:-1]) + " and " + nsybdays[-1]} have birthdays in the summer.')

If you do care about the serial comma and don't know that each list has at least two elements, you could try 

print(f'{", ".join(sybdays[:-1])}{"," if len(sybdays) > 2 else "" }{" and " if len(sybdays) > 1 else ""}{sybdays[-1]} {"have school year birthdays" if len(sybdays) != 1 else "has a school year birthday"}.')

print(f'{", ".join(nsybdays[:-1])}{"," if len(nsybdays) > 2 else ""}{" and " if len(nsybdays) > 1 else ""}{nsybdays[-1]} {"have birthdays" if len(nsybdays) != 1 else "has a birthday"} in the summer.')

[MOD: added ```python formatting -cf]

amandae
amandae
15,727 Points

Thank you! I wondered if it was something like that, or if it had become a built-in. I appreciate the code examples.

jb30 and Chris Freeman - Thank you, again! I got the code to work with a combination of your ideas.

Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 Points

I had a similar idea:

if len(sybdays) < 3:
    # name1
    # name1 and name2
    print(" and ".join(sybdays))
else:
    # name1, name2,  and name3
    print(", and ".join([", ".join(sybdays[:-1]), sybdays[-1]]))