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Using 'Or'

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  Using 'Or' Kitten Corner <joshua.shapo@gmail.com> - 2016-01-15 15:24 -0500
    Re: Using 'Or' Christian Gollwitzer <auriocus@gmx.de> - 2016-01-16 12:03 +0100
      Re: Using 'Or' Marko Rauhamaa <marko@pacujo.net> - 2016-01-16 14:41 +0200
    Re: Using 'Or' Alister <alister.ware@ntlworld.com> - 2016-01-16 14:06 +0000
      Re: Using 'Or' Steven D'Aprano <steve@pearwood.info> - 2016-01-17 08:53 +1100
        Re: Using 'Or' Alister <alister.ware@ntlworld.com> - 2016-01-16 22:47 +0000
          Re: Using 'Or' Bernardo Sulzbach <mafagafogigante@gmail.com> - 2016-01-16 21:12 -0200
          Re: Using 'Or' Chris Angelico <rosuav@gmail.com> - 2016-01-17 10:15 +1100

#101797 — Using 'Or'

Hi, I have python version 3.5.1 and I am working on a project, I'm trying
to make it by using the 'or' sequence, I'm trying to make it do 1 thing or
the other, here's an example: print('i like pie' or 'i like donuts'), it
only does the thing that's before the 'or', please help!

From,
Kitten Corner

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#101800

Am 15.01.16 um 21:24 schrieb Kitten Corner:
> Hi, I have python version 3.5.1 and I am working on a project, I'm trying
> to make it by using the 'or' sequence, I'm trying to make it do 1 thing or
> the other, here's an example:

> print('i like pie' or 'i like donuts')

> it only does the thing that's before the 'or', please help!

I think you misunderstand what "or" does. It evaluates the first 
expression, and if this is false, it evaluates the second. The empty 
string is considered false in Python, so, if you modfiy your example:

	print('' or 'i like donuts')

it'll print the second thing 'i like donuts'.

'or' does not choose randomly between both sides - if you are looking 
for that, check

 >>> import random
 >>> random.choice(('donuts','apples'))
'donuts'
 >>> random.choice(('donuts','apples'))
'apples'
 >>> random.choice(('donuts','apples'))
'donuts'
 >>>


	Christian

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#101803

Christian Gollwitzer <auriocus@gmx.de>:

> Am 15.01.16 um 21:24 schrieb Kitten Corner:
>> print('i like pie' or 'i like donuts')
>
>> it only does the thing that's before the 'or', please help!
>
> I think you misunderstand what "or" does. It evaluates the first
> expression, and if this is false, it evaluates the second.

The fact that "or" doesn't return True but one of its arguments is a
great feature. Too bad "any" doesn't follow suit:

   >>> any(x for x in ('a', 'b'))
   True

>>>> import random
>>>> random.choice(('donuts','apples'))
> 'donuts'

Well, there's that. "Any" works more nicely with generators, though.


Marko

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#101808

On 15/01/16 20:24, Kitten Corner wrote:
> Hi, I have python version 3.5.1 and I am working on a project, I'm trying
> to make it by using the 'or' sequence, I'm trying to make it do 1 thing or
> the other, here's an example: print('i like pie' or 'i like donuts'), it
> only does the thing that's before the 'or', please help!
>
> From,
> Kitten Corner
>

Conditional operators (or and not == etc.) need to be used in a test

how else would you expect you print statement to be able to decided 
which to print?

see if you can work through the code below

food="input food ?"
if food =='pie' or food=='donuts':
	print ('I like %s'%food)
else:
	print ('I dont like %s'%food'

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#101818

On Sun, 17 Jan 2016 01:06 am, Alister wrote:

> Conditional operators (or and not == etc.) need to be used in a test

Technically, that is incorrect.

> how else would you expect you print statement to be able to decided 
> which to print?


default = "I like Brussels sprouts."
message = random.choice(["", "I like boiled cabbage."])
print( message or default )



-- 
Steven

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#101822

On 16/01/16 21:53, Steven D'Aprano wrote:
> On Sun, 17 Jan 2016 01:06 am, Alister wrote:
>
>> Conditional operators (or and not == etc.) need to be used in a test
>
> Technically, that is incorrect.
yes but the op is confused in his usage enough at present
>
>> how else would you expect you print statement to be able to decided
>> which to print?
>
>
> default = "I like Brussels sprouts."
> message = random.choice(["", "I like boiled cabbage."])
> print( message or default )
>
>
>
I hope I never see production code like that

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#101824

On Sat, Jan 16, 2016 at 8:47 PM, Alister <alister.ware@ntlworld.com> wrote:
>>
>> default = "I like Brussels sprouts."
>> message = random.choice(["", "I like boiled cabbage."])
>> print( message or default )
>>
>>
>>
> I hope I never see production code like that
>

I agree. If you are going to use spaces after '(' and before ')' at
least be consistent.

-- 
Bernardo Sulzbach

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#101825

On Sun, Jan 17, 2016 at 9:47 AM, Alister <alister.ware@ntlworld.com> wrote:
> On 16/01/16 21:53, Steven D'Aprano wrote:
>>
>> On Sun, 17 Jan 2016 01:06 am, Alister wrote:
>>
>>> Conditional operators (or and not == etc.) need to be used in a test
>>
>>
>> Technically, that is incorrect.
>
> yes but the op is confused in his usage enough at present

Adding a falsehood sometimes helps reduce the confusion, but in this
case it just worsens things, I think.

>>> how else would you expect you print statement to be able to decided
>>> which to print?
>>
>>
>>
>> default = "I like Brussels sprouts."
>> message = random.choice(["", "I like boiled cabbage."])
>> print( message or default )
>>
>>
>>
> I hope I never see production code like that

Why? Okay, maybe not with a random.choice, but what about dict lookup?

specific_messages = {
     "foo": "You use a new foo.",
    "bar": "You sing a few bars of music.",
}
print(specific_messages.get(kwd) or "You {} vehemently.".format(kwd))

Seems fine to me.

ChrisA

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