How can you make it simpler?

[snippsat]

Use

Python program that can give me a random 4 digit number without digit repetition

Use random.sample().

>>> import random
>>> 
>>> random.sample(range(10), 4)
[6, 8, 9, 7]
>>> random.sample(range(10), 4)
[7, 6, 2, 3]
>>> random.sample(range(10), 10)
[0, 4, 9, 2, 6, 8, 1, 7, 3, 5]
>>> random.sample(range(10), 10)
[8, 4, 6, 9, 5, 0, 1, 2, 7, 3]