[Tutor] totalViruses[i] /= float(numTrials),

[Dave Angel]

On 04/24/2013 06:58 PM, Oscar Benjamin wrote:
> On 24 April 2013 23:41, Alan Gauld <alan.gauld at btinternet.com> wrote:
>> On 24/04/13 20:32, Oscar Benjamin wrote:
>>>
>>> On 24 April 2013 20:07, Alan Gauld <alan.gauld at btinternet.com> wrote:
>>>>
>>>> On 24/04/13 16:52, Dave Angel wrote:
>>>>
>>>>>> Does it mean? ;  totalViruses[i] = totalViruses[i]/float(numTrials)
>>>>>>
>>>>> As the others have said, that's exactly right, at least if
>>>>> totalViruses[i] is immutable, like an int or a float.
>>>>
>>>> What difference does immutability make here?
>>

Thanks for your help Oscar.  I was trying to keep it simple for a 
beginner.  So I deliberately did not elaborate on the exception.  But 
the one I had in mind was the behavior of a list, when += is used.

a = [1,2,3]
b = a
b += [4]     versus     b = b + [4]

The former would change a, while the latter would not.

If += were a literal substitution, like a macro, then this distinction 
could not happen.

So all I said was for immutables (and int and float are immutable), the 
statement was true.



-- 
DaveA