"""Input validation
This program adds input validation to :py:mod:`.P01_make_collatz_seq`
Add try and except statements to the previous project to detect whether
the user types in a noninteger string. Normally, the :obj:`int` function will
raise a :class:`ValueError` error if it is passed a noninteger string, as in `int('puppy')`.
In the except clause, print a message to the user saying they must enter an integer.
"""
[docs]def main():
from .P01_make_collatz_seq import collatz
try:
n = int(input("Input a number: "))
while n != 1:
print(n)
n = collatz(n)
print(n) # When n == 1
except ValueError:
print("Error: Input must be an integer.")
if __name__ == "__main__":
main()