check input value python code example

Example 1: how to say that an input needs to be a number python

try:
   val = int(userInput)
except ValueError:
   print("That's not an int!")

Example 2: python check if input() gives error

try:
    # Note: Python 2.x users should use raw_input, the equivalent of 3.x's input
    age = int(input("Please enter your age: "))
except ValueError:
    print("Sorry, I didn't understand that.")
else:
	if age >= 18: 
    	print("You are able to vote in the United States!")
	else:
    	print("You are not able to vote in the United States.")

Example 3: python double check if wants to execute funtion

while True:
    data = input("Please enter a loud message (must be all caps): ")
    if not data.isupper():
        print("Sorry, your response was not loud enough.")
        continue
    else:
        #we're happy with the value given.
        #we're ready to exit the loop.
        break

while True:
    data = input("Pick an answer from A to D:")
    if data.lower() not in ('a', 'b', 'c', 'd'):
        print("Not an appropriate choice.")
    else:
        break