How to replace elements in list with random number

Question

Firstly, I'm a python beginner and just stuck at simple thing.

I want to replace some of my elements in a list with randomly created numbers (by index), according to my values in another list.

Expected output will be like: [3,2,2,1,3]

My code at below totally doesn't work in the way it should.

ori = [4,1,2,1,3]   # some elements inside need to be changed 
num_list = [2,1,1,1]    # numbers that represent index in ori

import random
for num in range(len(num_list)):
    ori[num-1]= random.randint(1,4)
    # I want to replace element with previous one from given index                                                                           
print(ori)

Why the range(len( if num_list is already the indices to modify? Probably you should not allow duplicate indices in num_list as well (e.g. use a set instead of a list) — tehhowch
– tehhowch, Commented Sep 29, 2019 at 14:43
Why index 1 is mentioned 3 times? How can you have expectations about the output of you use random? — balderman
– balderman, Commented Sep 29, 2019 at 14:45
Erm...I mean to go through every item in num_list to get the values for modifying — mint
– mint, Commented Sep 29, 2019 at 14:49
The value 1 is duplicated, and it should take only one of them for modifying. The expected output I give is just an example, just to mention that I want [0] and [1] value to be changed — mint
– mint, Commented Sep 29, 2019 at 14:55

Timothée Dautrême · Accepted Answer · 2019-09-29 15:06:29Z

2

I don't know what you want to do but it seems to be good with this code. Why num_list contain number "1" 3 times ? In this code it will replace ori[1] by a random number 3 times... Ok for ori[2] will be randomized one time.

ori = [4,1,2,1,3]   # some elements inside need to be changed 
num_list = [2,1,1,1]    # numbers that represent index in ori

import random
for num in num_list:
    ori[num]= random.randint(1,4)
print(ori)

answered Sep 29, 2019 at 15:06

Timothée Dautrême

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Comments

Anog · Accepted Answer · 2019-09-29 15:22:32Z

0

The problem you have is that the num variable you declare is just the position in num_list, so here you will change ori at positions 0, 1, 2, 3 (which is what will be represented by your range).

You would fix your code like this:

ori = [4,1,2,1,3]   # some elements inside need to be changed 
num_list = [2,1,1,1]    # numbers that represent index in ori

import random
for num in num_list:
    ori[num-1]= random.randint(1,4)

answered Sep 29, 2019 at 15:22

Anog

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