使用“如果”再次运行循环？

Question

I am producing 2 arrays of random numbers that range from -3 to 3 (this would provide to be my x and y coordinates per say). However I want to produce a new set of numbers if the respective x and y is greater than my radius (which is 3) by using an if loop? What do I put in after my if loop to achieve this?

from physics import *
import random
N=3

x= zeros(N,float)
y= zeros(N,float)

for i in range (0, N):
    x[i] = uniform(6)-3
    y[i] = uniform(6)-3
    if (x[n]*2+y[n]**2)**0.5 > 3:

Thanks

Answer 1

Can't you just create a new range and then reset your index?

from physics import *
import random
N=3

x= zeros(N,float)
y= zeros(N,float)

for i in range (0, N):
    x[i] = uniform(6)-3
    y[i] = uniform(6)-3
    if (x[n]*2+y[n]**2)**0.5 <= 3:
        x = random.sample(range(-3, 3), n)
        y = random.sample(range(-3, 3), n)
        i = 0

Answer 2

Most random library modules provide a routine to return a floating point number from a uniform distribution over the interval [0,1). To choose randomly from a uniform distribution over the interval [a,b), where b > a, you can just multiply by ba , and then add a .

I'm not certain which modules you're importing in your example, so I'll give examples using the standard random module, as well as the numpy.random

random

import random
def rand_range(a, b):
   return a + random.uniform() * (b - a)

x = [rand_range(-3, 3) for i in range(3)]
y = [rand_range(-3, 3) for i in range(3)]

numpy.random

Numpy allows one to vectorize operations for speed and clarity.

import numpy as np
def rand_range(a, b, size):
    return a + np.random.random(size) * (b - a)

x = rand_range(-3, 3, (3))
y = rand_range(-3, 3, (3))

or, create an 2D array of 2 rows of 3 elements, and use unpacking

x, y = rand_range(-3, 3, (2, 3))

bounds checking

In order to ensure the points generated meet the criteria of being with 3 units of x, y = (0, 0), you can do something like the following:

x = []
y = []
for i in range(3):
   xi, yi = 3, 3    #initally set candidates to fail check
   while xi ** 2 + yi ** 2 > 9:
      xi = rand_range(-3, 3)
      yi = rand_range(-3, 3)
   x.append(xi)
   y.append(yi)

Given the underlying random method returns a value on the interval [0,1), these arrays should all pass the following assertion:

for xi, yi in zip(x,y):
   assert xi**2 + yi**2 <= 9

Answer 3

@mtadd

I am answering my question because I found a way to solve it. However, I'm curious whether the way you solved it is more efficient than my process mtadd.

In my physics import is where the random and numpy module are stored, hence why it isn't used in my code.

from physics import *

N=3 #Number of point charges

x= zeros(N,float) #grid
y= zeros(N,float)
i=0
for i in range (0, N): #Loop to ensure two values are <= 3
    while i < N:
        x[i] = uniform(6)-3
        y[i] = uniform(6)-3
        if x[i] ** 2 + y[i] ** 2 <= 9:
            i+=1
        else:
            i=0

print x,y

Thanks for the help guys