There are two ways to do keep asking for user input in Python. First using while true with if statement and break statement.
while True: # Loop continuously
inp = input() # Get the input
if inp == "": # If it is a blank line...
break # ...break the loop
Another way is using a while loop with condition expression.
inp = input() # Get the input
while inp != "": # Loop until it is a blank line
inp = raw_input() # Get the input again
Note: this code support Python 3.x, you will need to use raw_input for the below versions.
Example keep asking for user input in Python
Simple example code continues asking the user for input until it is considered valid.
Example 1
Input is taken as a string by default.
pw = '123'
while True:
number = input("Enter the Password: ")
if number == pw:
print("GOT IT")
break
else:
print("Wrong try again")
Output:

Example 2
number = ""
while number != '123':
number = input("Enter the Password: ")
Output:
Enter the Password: 1
Enter the Password: 123
Do comment if you have any doubts or suggestions on this Python input program.
Note: IDE: PyCharm 2021.3 (Community Edition)
Windows 10
Python 3.10.1
All Python Examples are in Python 3, so Maybe its different from python 2 or upgraded versions.

Degree in Computer Science and Engineer: App Developer and has multiple Programming languages experience. Enthusiasm for technology & like learning technical.