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Python - How to check if input is a number (given that input always returns strings)
I need to check a input and send a error message if it's not numerical. How would i do this the best way? Cant seem to find any other posts about it thou i'm shure someone must have asked this question before.
if not value.isdigit(): raise ValueError("Input must be numeric") @TokenMacGuy's solution is better if you're getting your input from raw_input(), but otherwise this works.
If you want to loop until you get proper input rather than raise an error, try this:
value = input("Input: ") while not value.isdigit(): input("Input must be numeric, please reenter: ") 
edit:
>>> while True: ... try: ... result = int(raw_input("Enter a Number: ")) ... break ... except ValueError: ... print "Input must be a number" ... Enter a Number: abc Input must be a number Enter a Number: def Input must be a number Enter a Number: 123 >>> result 123 >>> 
while True: user_input = raw_input("> Please enter a number:") try: n = float(user_input) except ValueError: continue else: break The isdigit function can be used to test if a string is all digits and is not empty:
val = '255' val.isdigit() 