numpy：通过随机不同选择索引来更改数组中的值

Question

I am new in numpy, and I am having troubles with simple managment of numpy arrays.

I am doing a task in which it said that randomly daily select different 12 items in a numpy by index to change its value.

import numpy as np
import random
N = 20
s = np.zeros([N])
for t in range(12):
    randomindex = random.randint(0,len(s)-1)
    s[randomindex] = 10

thanks for u answering.I'm sorry for my describing,i'm not good at how writting problem of python by english.--..I will give more detailed information

e.g. s=(1,2,3,4,5,6，7，8，9，10，11，12，13，14，15，16，17，18，19，20) 

and i randomly choose a item from its numpy by its index,

randomindex=random.randint(0,len(s)-1),

randomindex will be 0-19,

and s(randomindex)=10,if the randomindex is 2 means s(2) is 10, s=(1,2,10,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20).

And if i want choose 3 items, i do 3 times'for',how can i everytimes choose different index changes its value in numpy. and daily which means i will give sum the new s and given to a new numpy R[T] like:

import numpy as np
import random
N = 20
s = np.zeros([N])
T=10 #DAY
R = np.zereos([T])
for t in range(T-1):
    R[T+1]=R[T]+R[T]*3
    for t in range(12):
        randomindex = random.randint(0,len(s)-1)
        s[randomindex] = 10
        R[T]=np.sum(s)

Answer 1

I'm having a little difficulty understanding what you're asking, but I think you want a way to be selecting different values in a randomized order. And the problem with the above code is that you may be getting duplicates.

I have two solutions. One, you can use the Python random library . The Python random.shuffle function will randomly shuffle all the values in an iterable (such as a list or array). You can then proceed to access them sequentially as you normally would. Here's an example of Random Shuffle.

list1 = ["Apple", "Grapes", "Bananas","Grapes"]
random.shuffle(list1)
print(list1)

The second solution doesn't involve the use of a library. You can simply make an addition into the code above. Create a new empty list, and every time you retrieve a value add it into this list. Also, whenever you retrieve a value check to see whether it's already located in the list. For instance, if you retrieve the value 5, add it to the list. If later on, you end up with the value 5 again, run a check through the list and you will find that 5 already exists in it. You can then reset that iteration and take input again.

You can append to a list with the following code.

newlist = ["Python", "Java","HTML","CSS"]
newlist.append("Ruby")
print(newlist)