[Python] Cycle changes list that it should not [duplicate]

I'm writing weights mutator for my neural network. "distribute_genome" function should slightly mutate best genome and return it.

import random
best_genome = [[1, 2, 3], [4, 5, 6]]
def distribute_genome():
unique_genom = best_genome
print(best_genome)
for i in range(len(unique_genom)):
for j in range(len(unique_genom)):
unique_genom[j] += random.randint(-2, 2) #mutation
print(best_genome)
print("does not work" if unique_genom == best_genome else "ok")
return unique_genom
print(distribute_genome())


But i noticed that best_genome being chanded when fuction runs. Soon i discovered that this loop changes it, if i delete the loop best_genome will stay same.

for i in range(len(unique_genom)):
for j in range(len(unique_genom)):
unique_genom[j] += random.randint(-2, 2) #mutation


I found out the reason of this error, and a question with the same problem but it still gives the same result, like here:

import random
best_genome = [[1, 2, 3], [4, 5, 6]]
def distribute_genome():
unique_genom = list(best_genome)
for i in range(len(unique_genom)):
for j in range(len(unique_genom)):
unique_genom[j] += random.randint(-2, 2) #mutation
return unique_genom

print("does not work" if distribute_genome() == best_genome else "works")
>does not work


How should i fix this?

Continue reading...