[Tutor] looping - beginner question

[Mats Wichmann]

On 03/02/2017 08:06 AM, Alan Gauld via Tutor wrote:
> On 02/03/17 13:42, Rafael Knuth wrote:
> 
>> bar = ["beer", "coke", "wine"]
>>
>> customer_order = input("What would you like to drink, dear guest? ")
>>
>> for drink in bar:
>>     if customer_order != drink:
>>         print ("Sorry, we don't serve %s." % customer_order)
>>     else:
>>         print ("Sure, your %s will be served in a minute!" % customer_order)
>>
>> What I want the program to do is to "silently" loop through the list
> 
> So you only want the sorry... message if the loop completes without
> finding a drink. That means you need to put that print statement after
> the loop. Python includes a feature for that - a for/else construct.
> 
> for drink in bar:
>     if drink == customer_order:
>        print(Sure...)
>        break  #exit loop and avoid else
> else:
>     # only if the loop completes normally
> 
> However, there is another way to do this that doesn't
> use an explicit loop: the 'in' operator
> 
> if customer_order in bar:
>     print("sure....)
> else:
>     print ("Sorry....)

To follow on to what Alan said, you don't need to loop over a list (or
tuple, or dictionary, or other "iterable") to find out if it contains an
item. You can just test membership directly.