[Tutor] Built In Functions

[Rafael Knuth]

got it!
Thanks, Peter

On Tue, Dec 17, 2013 at 4:27 PM, Peter Otten <__peter__ at web.de> wrote:
> Rafael Knuth wrote:
>
>> Hej there,
>>
>>> I use any() and all() frequently. For example, suppose you have a
>>> function that takes a list of numbers, and they are all supposed to be
>>> positive.
>>>
>>> def calculate_values(numbers):
>>>     if all(number > 0 for number in numbers):
>>>         # do the calculation
>>>     else:
>>>         raise ValueError("negative or zero number found")
>>>
>>> That could be re-written as:
>>>
>>> def calculate_values(numbers):
>>>     if any(number <= 0 for number in numbers):
>>>         raise ValueError("negative or zero number found")
>>>     else:
>>>         # do the calculation
>>
>> Got it. I played with the examples above, I wrote wrote two functions
>> and they work nicely.
>> I understand now why it makes sense to use all() and any():
>>
>> def check_values(a, b):
>>     if all(number >= 0 for number in range(a, b)):
>>         return True
>>     else:
>>         raise ValueError("negative number")
>>
>> And:
>>
>> def check_values(a, b):
>>     if any(number >= 0 for number in range(a, b)):
>>         return True
>>     else:
>>         raise ValueError("negative number")
>>
>> But what if I have to check multiple values within one function? I am
>> able to get the task done with a plain vanilla if statement. In the
>> exemplary function below the user is expected to enter only positive
>> numbers and in case he provides a negative number, a ValueError is
>> raised:
>>
>> def PositiveCalculator(a, b):
>>     if a > 0 and b > 0:
>>         return a + b
>>     else:
>>         raise ValueError("negative number")
>>
>> In this function one negative number is tolerated:
>>
>> def PositiveCalculator(a, b):
>>     if a > 0 or b > 0:
>>         return a + b
>>     else:
>>         raise ValueError("negative number")
>>
>> How would I have to modify these two functions if I wanted to use the
>> all( ) or any() function respectively?
>
> The first one could become
>
> def positive_calulator(a, b):
>     summands = a, b
>     if all(x > 0 for x in summands):
>         return sum(summands)
>     raise ValueError("negative argument encountered")
>
> You can make that work with and arbitrary number of arguments (and save a
> line of code):
>
> def positive_calculator(*summands):
>     if all(x > 0 for x in summands):
>         return sum(summands)
>     raise ValueError("negative argument encountered")
>
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