Random generator function in Python

Question

I have been learning Java since September, but have been given an assignment for a science course by a professor to create a program in Python that will generate a random diameter using a max and minimum value, and 15 random points within this sphere (x, y, z).

I need to make a random number generator that generates a number between 0.0 and 1.0 so I can plug it into my formula to find a random diameter. If the random number is RN, it would be: [(RN*(max-min))+min]

At first I used this random function:

from random import*
RN=random():

The problem is, this random function is [0.0, 1.0). In other words, it does not include 1.0. How can I create a function that includes 1.0?

Also, if you don't mind, can you help me with finding the y and z coordinates? I know how to find x.

The formula for the y value is y=+ or - sqrt(r^2-x^2) (to be randomly generated too). I would have the x value, which is the result from the random function [0.0-1.0], and the radius which would be half my diameter. I am a complete beginner at Python, how do I initialize my x and y and put the above formula in?

The formula for z is similar, z=+ or - sqrt(-x^2-y^2+r^2) (to be randomly generated as well)

These are using the formulas for a circle: radius: r=sqrt(x^2+y^2) sphere:r=sqrt(x^2+y^2+z^2)

I would be incredibly grateful if you could answer any part of my question, thank you so much for taking the time to read this!! **by the way, I am usinHi! I have been learning Java since September, but have been given an assignment for a science course by a professor to create a program in Python that will generate a random diameter using a max and minimum value, and 15 random points within this sphere (x, y, z).

I need to make a random number generator that generates a number between 0.0 and 1.0 so I can plug it into my formula to find a random diameter. If the random number is RN, it would be: [(RN*(max-min))+min]

At first I used this random function:

from random import* RN=random():

The problem is, this random function is [0.0, 1.0). In other words, it does not include 1.0. How can I create a function that includes 1.0?

Also, if you don't mind, can you help me with finding the y and z coordinates? I know how to find x.

The formula for the y value is y=+ or - sqrt(r^2-x^2) (to be randomly generated too). I would have the x value, which is the result from the random function [0.0-1.0], and the radius which would be half my diameter. I am a complete beginner at Python, how do I initialize my x and y and put the above formula in?

The formula for z is similar, z=+ or - sqrt(-x^2-y^2+r^2) (to be randomly generated as well)

These are using the formulas for a circle: radius: r=sqrt(x^2+y^2) sphere:r=sqrt(x^2+y^2+z^2)

I would be incredibly grateful if you could answer any part of my question, thank you so much for taking the time to read this!!!

**by the way, I am using python x,y spyder!

score 1 · Answer 1 · edited Apr 13 '17 at 12:19

random.uniform will give you a uniformly distributed random number between a given minimum and maximum.

Just generate random points and check if they are within the sphere. If they are not, discard them and try again.

import math
import random

def generate_points(n_points, min_diameter=0, max_diameter=1):
    diameter = random.uniform(min_diameter, max_diameter)
    radius = diameter / 2
    count = 0
    while count < n_points:
        x, y, z = [random.uniform(-radius, radius) for _ in range(3)]
        distance = math.sqrt(x * x + y * y + z * z)
        if distance <= radius:
            yield (x, y, z)
            count += 1

for x, y, z in generate_points(10):
    print x, y, z

Note: this may bias what points are generated. (I'm not sure, it's probably okay actually.) Another approach might be to use polar coordinates, choosing two random angles and a random radius (offset from center).

Here is the math for that approach:

theta = random.uniform(0, 2 * math.pi)
phi = random.uniform(-math.pi / 2, math.pi / 2)
x = r * cos(theta) * cos(phi)
y = r * sin(phi)
z = r * sin(theta) * cos(phi)

See here for more on distribution:

https://math.stackexchange.com/questions/87230/picking-random-points-in-the-volume-of-sphere-with-uniform-probability

http://mathworld.wolfram.com/SpherePointPicking.html (this one is about points on the surface of the sphere, so might not be as useful)

score 1 · Answer 2 · answered Jun 08 '16 at 10:50

I used this for a random generator and it works, i'm not sure if it's the right one you're looking for but I hope it helps

import random

maths_operator_list=['+','-','*']
maths_operator = random.choice(maths_operator_list)
number_one = random.randint(0,20)
number_two = random.randint(0,20)
correct_answer = 0

print(str(number_one), str(maths_operator), number_two)

if maths_operator == '+':
    correct_answer = number_one + number_two
elif maths_operator == '-':
    correct_answer = number_one - number_two
elif maths_operator == '*':
    correct_answer = number_one * number_two

print(correct_answer)

score 0 · Answer 3 · 2013-11-21T00:36:01.230

0

As answer to the random number generator :

RN = random.uniform(a, b)

Return a random integer N such that a <= N <= b.

As how to initiate x and y, y will be initialize when you set y = to something, it does it automatically.

edited Nov 21 '13 at 00:36

answered Nov 21 '13 at 00:29

score 0 · Answer 4 · answered Nov 21 '13 at 00:33

0

You can use random.range

random.randrange(-15,15,.1)

That will find a number between -15 and 15 that is divisible by 0.1.

answered Nov 21 '13 at 00:33

1

`random.randrange` can only have integer arguments. The better way to do this (in my opinion) is `random.randrange(-150, 150, 1)/10`. – Rushy Panchal Nov 21 '13 at 01:08

Random generator function in Python

4 Answers4