If else statement does not give desired output

Question

from datetime import date
import calendar

my_date = date.today()
today_day = calendar.day_name[my_date.weekday()]

if today_day == 'Wednesday' or 'Thursday':
    place = 'A'
else:
    place = 'B'

Initially, I wanna set place as 'A' when 'today' is 'Wednesday' or 'Thursday', otherwise as 'B'. But the designed code kept returning 'A' despite it is 'Saturday' today(14/10/2017). How could I fix it?

Replace your if statement with `if today_day in ['Wednesday', 'Thursday']` — Yaroslav Surzhikov, Oct 14 '17 at 13:09

score 2 · Answer 1 · answered Oct 14 '17 at 13:07

Change your condition to:

if today_day == 'Wednesday' or  today_day == 'Thursday':

or:

if today_day in ('Wednesday', 'Thursday'):

In your version 'Thursday' is a non-empty string and as such always truthy when evaluated as an atomic part of a boolean expression.

Udo Klein · Answer 2 · 2017-10-14T13:35:57.860

2

Your if statements is eqivalent to

if (today_day == 'Wednesday') or 'Thursday':

and False or 'none empty string' will always evaluate as True.

I would implement this as

weekday = date.today().weekday()
place = 'A' if weekday in [3,4] else 'B'

edited Oct 14 '17 at 13:35

answered Oct 14 '17 at 13:08

Udo Klein

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score 2 · Answer 3 · answered Oct 14 '17 at 13:09

What you have written is equivalent to boolean or of two conditions

(today_day == 'Wednesday') or 'Thursday'

Thursday always evaluates to True (because that's how non-empty strings are evaluated in python).

Instead, you could write the (more idiomatic)

today_day in ('Wednesday' or 'Thursday')

or

today == 'Wednesday' or today == 'Thursday'

score 0 · Accepted Answer · answered Oct 14 '17 at 13:08

The issue is you are asking if (today_day == 'Wednesday') or 'Thursday'. 'Thursday' evaluates to True since it is not an empty string, so place will always be A. What you need to do is

if today_day == 'Wednesday' or today_day == 'Thursday':
    place = 'A'
else:
    place = 'B'

If else statement does not give desired output

4 Answers4