My function returns a list with a single integer in it, how can I make it return only the integer?

Question

How do I remove the brackets from the result while keeping the function a single line of code?

day_list = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"]

def day_to_number(inp):
    return [day for day in range(len(day_list)) if day_list[day] == inp]

print day_to_number("Sunday")
print day_to_number("Monday")
print day_to_number("Tuesday")
print day_to_number("Wednesday")
print day_to_number("Thursday")
print day_to_number("Friday")
print day_to_number("Saturday")

Output:

[0]
[1]
[2]
[3]
[4]
[5]
[6]

Answer 1

The list comprehension is overkill. If your list does not contain duplicates (as your sample data shows, just do)

>>> def day_to_number(inp):
...     return day_list.index(inp)
... 
>>> day_to_number("Sunday")
0

I would also advice to make the day_list an argument of the function, i.e.:

>>> def day_to_number(inp, days):
...     return days.index(inp)
... 
>>> day_to_number("Sunday", day_list)
0

Looking it up in the global name space is a bit ugly.

And to make the whole thing more efficient (list.index is O(n)) use a dictionary:

>>> days = dict(zip(day_list, range(len(day_list))))
>>> days
{'Monday': 1, 'Tuesday': 2, 'Friday': 5, 'Wednesday': 3, 'Thursday': 4, 'Sunday': 0, 'Saturday': 6}
>>>
>>> def day_to_number(inp, days):
...     return days[inp]
... 
>>> day_to_number("Sunday", days)
0