Debugging reason for python running unreasonably slow when adding numbers

[Edmondo Giovannozzi]

> > def sum1(): 
> >     s = 0 
> >     for i in range(1000000): 
> >         s += i 
> >     return s 
> > 
> > def sum2(): 
> >     return sum(range(1000000))
> Here you already have the numbers you want to add. 

Actually using numpy you'll be much faster in this case:

§ import numpy as np
§ def sum3():
§    return np.arange(1_000_000, dtype=np.int64).sum()

On my computer sum1 takes 44 ms, while the numpy version just 2.6 ms
One problem is that sum2 gives the wrong result. This is why I used np.arange with dtype=np.int64.

sum2 evidently doesn't uses the python "big integers" e restrict the result to 32 bits.