CODEWITHSUNDEEP
python
Daniel Andrews
Daniel Andrews

Reputation: 43

List is out of range why?

Every time I input 1 it will say list index out of range I ended up putting a if statement that said if input is 1 print January How can I make this program work with out the first if statement

months= ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" ]
months_nums=[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
user_input= int(input("Enter month: "))
while user_input != 0:
    for i in months_nums:
        if user_input == months_nums[i]:
            print(months[i])
            break
    user_input= int(input("Enter months: "))

Upvotes: 1

Views: 60

Answers (5)

Anton vBR
Anton vBR

Reputation: 18914

Instead of creating a list why not use the datetime library:

import datetime

user_input = int(input("Enter month: "))

while user_input != 0: 
    month = datetime.datetime.strptime(str(user_input),"%m")
    print(month.strftime("%B"))
    user_input= int(input("Enter months: "))

Basically you can read more about strftime which prints a datetime object in a specific way: e.g. datetime.strftime("%B") gives month. You also need strptime which reads a date from a string, e.g. datetime.strptime("31/12/1999","%d/%m/%Y"),and we only need to read the month in this case.

However, I would probably check if input is an integer and then check if it is within the range 1-12 if not quit. Something like this this:

import datetime

# Start a loop
while True:

    # Ask for a number until you get one
    while True:
        user_input= input("Enter months: ")
        try:
            user_input = int(user_input)
            break
        except ValueError:
            print("you must enter an integer")

    # Break if user input not in range
    if user_input not in range(1,12):
        break

    # Get current month    
    month = datetime.datetime.strptime(str(user_input),"%m")

    # Print
    print(month.strftime("%B"))

Upvotes: 0

atru
atru

Reputation: 4744

If you are simply looking to print the month name based on a continuously prompted user input, why not use this?

user_input= int(input("Enter month: "))

while user_input != 0:
    print(months[user_input-1])
    user_input= int(input("Enter months: "))

This takes advantage of the order in the array month - month name index in that array is simply the input number - 1.

The reason why your loop didn't work is actually a small and not that visible bug. for i in months_nums: means you're literally fetching the elements of months_nums, not indices. In other words i = 1,2,3,..,12 not 0,1,2,..11.

When looking for January you ask for the first element which is never found because i in months_nums[i] will never have a value 0 and fetch you month number 1. On the other hand it will eventually reach value 12 and the last index of month_nums is 11 - which is when it throws an error.

You can fix this issue in your original loop by using i as elements which they actually are, rather then indices in the if statement:

user_input= int(input("Enter month: "))
while user_input != 0:
    for i in months_nums:
        if user_input == i:
            print(months[i-1])
            break
    user_input= int(input("Enter months: "))

This one still takes advantage of ordering in months so the printed value has an index of i-1.

Upvotes: 1

Deja
Deja

Reputation: 356

months= ["January", "February", "March", "April", "May", "June", "July", 
        "August", "September", "October", "November", "December" ]
months_nums=[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
user_input= int(input("Enter month: "))
while user_input != 0:
for i in months_nums:
    if user_input == i:
        print(months[i-1])
        break
user_input= int(input("Enter months: "))

Upvotes: 0

Dharmesh Fumakiya
Dharmesh Fumakiya

Reputation: 2338

months= ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" ]
months_nums=[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
user_input= int(input("Enter month: "))
while user_input != 0:
    if user_input in months_nums:
        print(months[user_input-1])
        break
    user_input= int(input("Enter months: "))

Upvotes: 0

Mike Tung
Mike Tung

Reputation: 4821

The issue has to do with the way you are iterating the indices and checking if a user's input matches the month in your months_num list.

if user_input == months_nums[i] wouldn't work because if a user inputs 1 months will be February cause lists count from 0.

Instead you should do the following:

months= ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" ]
months_nums=[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]

options = dict(zip(months_num, months))

user_input= int(input("Enter month: "))

try:
    print(options[user_input])
except KeyError as e:
    print(e)

Upvotes: 0

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