Understanding how reassignment works

[Shreya10o]

I tried the following code, the for loop was not changing the original variables but only printing out the changed results. Meaning, when I printed out list4[0], it was giving the correct outcome, but not when I print out the variable in list4[0], ie,labels01112. But a reassignment of list4 changed the original variables as well. So my question is, before this reassignment, when we printed out these variables, they weren't changed, and we are assigning these unchanged variables to list4, then how is the reassignment changing the them?

labels01112=np.array([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0, 0, 0])

centers01112=np.array([[ 0.01943914,  0.01259848, -0.12696217],
       [-0.9525181 , -0.61732533,  6.22114648]])

length01112=np.array([0.12905811, 6.32384731])

labels11112=np.array([1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 1, 1, 1, 0,
       0, 1, 0, 1, 1, 0, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1,
       1, 0, 0, 0, 0, 1])

centers11112=np.array([[-0.57971121, -0.67466955, -0.63219157],
       [ 0.49382807,  0.57471851,  0.53853356]])

length11112=np.array([1.09128836, 0.92961601])

list3=([centers01112, length01112],
[centers11112, length11112])

z=[]
for i in range(len(list3)):
  if (len([j for j in list3[i][0][0] if j < 0])<(len(list3[i][0][0])/2)) & (len([i for i in list3[i][0][1] if i < 0])>(len(list3[i][0][1])/2)):
     z.append('turn opp')
  elif (len([j for j in list3[i][0][0] if j < 0])>(len(list3[i][0][0])/2)) & (len([i for i in list3[i][0][1] if i < 0])<(len(list3[i][0][1])/2)):
     z.append('keep same')
z

Output:
['turn opp', 'keep same']

list4=[labels01112, labels11112]
for i in range(len(list4)):
  if z[i]=='turn opp' :
    idx = [1,0]
    lut = np.zeros_like(idx)
    lut[idx] = np.arange(2)
    list4[i]=lut[list4[i]]
    print(list4[i])

Output:
[1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
 1 1 1 1 1 1 1 1 1 1 1 1 1]

list4[0]

Output:
array([1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1,
       1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
       1, 1, 1, 1, 1, 1])

labels01112

Output:
array([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
       0, 0, 0, 0, 0, 0])

labels01112, labels11112 = list4
labels01112

Output:
array([1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 1,
       1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
       1, 1, 1, 1, 1, 1])