A "while-except" loop, in which it acts like a do-while loop from other languages, except the condition is "did an exception occur during the execution of the iteration". One could specify a type of exception at the top, similar to an except block header. (sorry, I'm an idiot)
Example (the keyword might be different):

# asks for a number until the user gives one properly, then
# calculates the square of it.
whexc ValueError:
    num = int(input("Enter a number: "))
print("The square of your number is " + str(num * num)) # assuming whexc works, this will not cause an error