I am trying to generate a function which generate random numbers from a uniform distribution Number_Rand()
and another one which generates a random number given a certain seed Number_Rand_Seed()
- so that it will always be the same for a fixed seed. However, I call the function Number_Rand_Seed()
inside Number_Rand()
, and for some reason the seed is also used to generate random numbers in Number_Rand()
, so that its output is always the same. Shouldn't the seed be a local variable inside Number_Rand_Seed()
? And shouldn't the seed be "renewed" everytime I call a np.random function (see, e.g., this answer)? What should I do then to "renew" the seed inside Number_Rand()
and ignore the seed of Number_Rand_Seed()
?
Here is an example:
def Number_Rand_Seed():
np.random.seed(300121)
a = np.random.uniform(0, 10)
return a
def Number_Rand():
a = Number_Rand_Seed()
b = np.random.uniform(0, 10)
return a, b
for i in range(3):
print(Number_Rand())
The output is
(9.354120260352017, 2.552916103146633)
(9.354120260352017, 2.552916103146633)
(9.354120260352017, 2.552916103146633)
but I wanted something like
(9.354120260352017, 8.823425849537022)
(9.354120260352017, 5.950595370176398)
(9.354120260352017, 9.992406389398592)
In recent numpy versions, you can create separate random number generators using np.random.default_rng
.
In the following I use that for a
, while retaining the default for b
:
In [35]: def Number_Rand_Seed():
...: rng = np.random.default_rng(300121)
...: a = rng.uniform(0, 10)
...: return a
...:
...: def Number_Rand():
...: a = Number_Rand_Seed()
...: b = np.random.uniform(0, 10)
...: return a, b
...:
...: for i in range(3):
...: print(Number_Rand())
...:
(9.98668624527619, 2.7036401003521817)
(9.98668624527619, 9.154952983315784)
(9.98668624527619, 1.413705001678095)
In [36]: Number_Rand()
Out[36]: (9.98668624527619, 5.274283695955279)
Or define a "default" rng
outside the function. The rng
in Number_Rand_Seed
is local, and doesn't interfere with the rng
defined outside it. Of course the code would be clearer to humans if I used different names.
...: rng = np.random.default_rng()
...: def Number_Rand():
...: a = Number_Rand_Seed()
...: b = rng.uniform(0, 10)
...: return a, b