0.45519596
0.94176289
0.14892619
0.9395088
0.5045557
Original array
Replace
0.45519596
-1.
0.14892619
0.9395088
0.5045557
0.45519596
0.94176289
0.94176289
0.14892619
0.9395088
0.5045557
Maximum value
Replaced by -1
np.random.random(5)
x[x.argmax()] = -1