在列表Python中选择元素

Question

I am trying to select elements in a list containing the number of days in each month and add those days onto a variable containing a total.

from datetime import date
months = [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
inmonth = str(float(input("month")))
intmonth = int(inmonth[0])
nowmonth = (date.today().month)
days = 0

if intmonth < nowmonth:
    for c in range(months[intmonth-1], months[nowmonth-1]):
        days = days + months[c]
print(days)

EDIT:

Ok, I fixed the issue with the input, however with this code nothing is being added to days, any ideas why?

Thanks.

Answer 1

In addition to the problem stated by Kieleth, your loop does not use the indices you expected. We are now in october ( nowmonth = 10 ), say I answer 4 for april.

for c in range(months[intmonth-1], months[nowmonth-1]):

gives intmonth-1 = 3 , months[intmonth-1] = 30 , nowmonth-1 = 9 , months[nowmonth-1] = 31 => c gets the value 30 !!!

So you code should be :

from datetime import date
months = [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
intmonth = int(input("month")) # fixes the problem stated by Kieleth
nowmonth = (date.today().month)
days = 0

if intmonth < nowmonth:
    for c in range(intmonth-1, nowmonth-1):
        days = days + months[c]
print(days)

But the method to find those kind or errors if quite simple : print is your friend !!!

If you simply had written:

from datetime import date
months = [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
inmonth = str(float(input("month")))
intmonth = int(inmonth[0])
print(inmonth, intmonth) # control input
nowmonth = (date.today().month)
days = 0

if intmonth < nowmonth:
    for c in range(months[intmonth-1], months[nowmonth-1]):
        print (c, days) # a spy per iteration
        days = days + months[c]
print(days)

it would have been evident that you did not go through the loop