[Tutor] Data persistence problem

[Wolfgang Maier]

Alan Gauld <alan.gauld <at> btinternet.com> writes:

> 
> On 21/06/13 07:21, Arijit Ukil wrote:
> > I have following random number generation function
> >
> > def*rand_int* ():
> >      rand_num = int(math.ceil (random.random()*1000))
> > returnrand_num
> >
> > I like to make the value of rand_num (return of rand_int) static/
> > unchanged after first call even if it is called multiple times.
> 
> The simple solution is to store the value in a global variable.
> 
> rand_num = None
> 
> def rand_int():
>     global rand_num
>     if not rand_num:
>        rand_num = int(math.ceil (random.random()*1000))
>     return rand_num
> 
> Or if you really don't like globals you could create
> a generator function:
> 
> def rand_int():
>     rand_num = int(math.ceil (random.random()*1000))
>     while True:
>        yield rand_num
> 
> Incidentally, any reason why you don't use the random.randint() function 
> rather than the int(ceil(...) stuff?
> 
> HTH

a more general solution for random number generation is to use random.seed()
with a fixed argument:

def rand_int (seed=None):
    random.seed(seed)
    rand_num = int(math.ceil (random.random()*1000))
    return rand_num

then call this with the same argument to obtain the same number. But as Alan
said using random.seed and random.randint is a much simpler choice.
Wolfgang