CODEWITHSUNDEEP
pythonrandomrange
Yashas
Yashas

Reputation: 1234

generate a random range between two numbers

What is the pythonic (can use numpy) way to generate a random range of length [range_length_min, range_length_max] in the range [range_start, range_end]?

Example:

Allowed Solutions:

Invalid Solutions:

Current Solution:

start = np.random.randint(range_start, range_end - (range_max_length - range_min_length))
end = start + np.random.randint(range_min_length, range_max_length)

This gives the correct result but does not sample uniformly. The range_end - (range_max_length - range_min_length) is a hack.

Upvotes: 0

Views: 292

Answers (3)

John Coleman
John Coleman

Reputation: 51988

Here is one approach, based on weighting the choice of the length:

import random

def rand_interval(lmin,lmax,a,b):
    """picks random subinterval in [a,b] with length between lmin and lmax inclusive"""
    weights = [b-a - x + 1 for x in range(lmin,lmax+1)]
    length = random.choices(range(lmin,lmax+1),weights)[0]
    start = random.randint(a,b-length)
    return start, start + length

A test:

import collections
print(collections.Counter(rand_interval(1,2,1,3) for _ in range(10000)))

typical output:

Counter({(1, 2): 3389, (1, 3): 3386, (2, 3): 3225})

Upvotes: 1

Vicrobot
Vicrobot

Reputation: 3988

Just try making a function for specific needs:

>>> def foo(range_start, range_end, range_length_min, range_length_max):
...     v = random.randint(range_start, range_end)
...     v1 = random.randint(v + range_length_min, v + range_length_max if range_length_max <= range_end else range_end)
...     return [v, v1]
... 
>>> foo(range_start, range_end, range_length_min, range_length_max)
[1384, 1390]

Upvotes: 0

Nick Antonopoulos
Nick Antonopoulos

Reputation: 146

How about?

from random import randint

a = randint(range_start, range_end - range_length_max)
b = randint(range_length_min, range_length_max)

r = [a, a+b]

Upvotes: 0

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