How to make last element of list finish with a dot and the others with a comma?

Question

I made this list with a for loop that points errors when yoy choose a name. I'd like to know how can I make it so that the last line finishes with '.' and the others finish with ';'.

while True:
    if len(errors_list) != 0:
        print("Your name has thesse errors::")
        for i in errors_list:
                print("     " + str(errors_list.index(i) + 1) + "- " + i + ".")
        print("Try again.")
        errors_list.clear()
        name = input("My name is ").title()
        choose_name(name)
    else:
        print("Nice to meet you, " + fname + " " + sname + ".")
        break

Result when I type a name like '--- ':

Your name has these errors:
     1- It has no letters.
     2- It has symbols.
     3- The last letter is a space.
Try again.
My name is

I'd like to make it so that 1 and 2 finish with ';' and 3 with '.'. Thanks!

can you show me the error list? – Parthik B. Jul 19 '19 at 10:56 — Parthik B., Jul 19 '19 at 10:56

Peilonrayz · Answer 1 · 2019-07-21T03:49:11.677

All the existing solutions so far seem pretty poor, this is as print is expensive to call.
errors_list.index(i) runs in O(n) time making your solution run in O(n^2) time. You can improve this, to O(n) time, by using enumerate.
You can also think of what you're doing simply as concatenating values of a list and adding a period.

I would use:

errors = [f'     {i}- {error}' for i, error in enumerate(errors_list, 1)]
print(';\n'.join(errors) + '.')

asikorski · Accepted Answer · 2019-07-19T11:55:38.233

0

Extending Roman Perekhrest's answer, enumerate has an optional parameter start:

errors_list = ['It has no letters', 'It has symbols', 'The last letter is a space']

for i, err in enumerate(errors_list, start=1):
    print("\t{}- {}{}".format(i, err, ';' if i < len(errors_list) else '.'))

additionaly with Python 3.6+ you can use f-strings instead of format:

errors_list = ['It has no letters', 'It has symbols', 'The last letter is a space']

for i, err in enumerate(errors_list, start=1):
    print(f"\t{i}- {err}{';' if i < len(errors_list) else '.'}")

edited Jul 19 '19 at 11:55

answered Jul 19 '19 at 11:40

asikorski

882
6
20

Thanks! Learned a lot with both your answers. I just don't get what's the 'start' parameter for. It seems to change nothing – Jul 19 '19 at 11:44
Glad to help! Remember to mark an answer as a solution if you think your problem is solved :) – asikorski Jul 19 '19 at 11:50
Also, for future readers: `start=1` changes the starting value that appears at the beginning of each line. Roman's solution starts counting from 0 and performs two redundant `i+1`'s on each iteration. – asikorski Jul 19 '19 at 11:51

score -1 · Answer 3 · answered Jul 19 '19 at 10:56

-1

Instead of:

for i in errors_list:
    print("     " + str(errors_list.index(i) + 1) + "- " + i + ".")

do

s = len(errors_list)
for e, i in enumerate(errors_list):
    ending = ";" if e + 1 < s else "."
    print("     " + str(errors_list.index(i) + 1) + "- " + i + ending)

EDIT: to those jumping to the gun - OP did write in a title comma, but he used semicolon (;) twice (!) in a question itself.

answered Jul 19 '19 at 10:56

Radosław Cybulski

2,952
10
21

Thanks! I already used one that's simpler though. Yes, I did write comma in the title because I'm not a native english speaker and I didn't remember the name for semicolon. – Jul 19 '19 at 11:28

score -1 · Answer 4 · answered Jul 19 '19 at 11:02

Simply with enumerate function:

errors_list = ['It has no letters', 'It has symbols', 'The last letter is a space']
...
for i, err in enumerate(errors_list):
    print("     {}- {}{}".format(i+1, err, ';' if i+1 != len(errors_list) else '.'))

The crucial loop will output:

    1- It has no letters;
    2- It has symbols;
    3- The last letter is a space.

How to make last element of list finish with a dot and the others with a comma?

4 Answers4