[Tutor] using datetime and calculating hourly average

[John [H2O]]

Alan Gauld wrote:
> 
> 
> I assume there is a good reason to use a numpy array instead of
> a regular list? ie You need a numpy array elsewhere in the code?
> I've never used numpy bt there is a possibility that array access
> is slower than list access, but I have no idea. It just adds an extra
> level of complexity thats all.
> 

Yes, I use numpy a lot, my understanding is that is is quite a bit faster
than lists... but perhaps not in a case like this.


>> As for your comment regarding the invariant... would it be:
>> while hr q:
>>
> 
> I think he meant
> 
> while hr <= q
> 
> as per your original code
> 
Okay, thanks!



> 
>>>>         ind = np.where( (X[:,0] > hr) & (X[:,0] < nhr) )
> 
> I have no idea what this is doing but do you really mean a bitwise
> and here? You are effectively bitwise anding two boolean values
> which seems odd to put it mildly...
> 

Well, effectively I am searching the array for values matching the criteria,
but maybe I don't understand the bitwise details. What I am trying to say
is:
" index = X where hr < X[:,0] < nhr "

I had problems though when I tried to code it as such:

ind = np.where((hr < X[:,0] < nhr)) 
this doesn't work, though you think it would...



> HTH,
> -- 
> Alan Gauld
> Author of the Learn to Program web site
> http://www.alan-g.me.uk/ 
> 

Yes, thank you.


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