[Tutor] Function question

[Peter O'Doherty]

Many thanks!

On 25-03-17 11:17, Alan Gauld via Tutor wrote:
> On 25/03/17 10:01, Peter O'Doherty wrote:
>
>> def myFunc(num):
>>       for i in range(num):
>>           print(i)
>>
>> print(myFunc(4))
>> 0
>> 1
>> 2
>> 3
>> None #why None here?
> Because your function does not have an explicit return
> value so Python returns its default value - None.
> So the print() inside the function body prints the 0-3
> values then the function terminates and returns the (default)
> None to your top level print.
>
>> def myFunc(num):
>>       for i in range(num):
>>           return i
>>
>> print(myFunc(4))
>> 0 #why just 0?
> Because return always returns from the function immediately.
> So you call the function, it enters the loop, sees the return for the
> first element and exits. The print() then prints that returned value.
>
> The preferred method to do what I think you were expecting is to build a
> list:
>
> def anotherFunction(num):
>      result = []
>      for i in range(num):
>         result.append(i)
>      return result
>
> Which is more concisely written using a list comprehension but
> that would hide the general point - that you should accumulate results
> in a collection if you want to return more than a single value.
>
> To print the result you would typically use the string.join()
> method:
>
> print(' '.join(anotherFunction(4))
>
>


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// Peter O'Doherty

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