def input_number(msg, err_msg=None):
while True:
try:
return float(raw_input(msg))
except ValueError:
if err_msg is not None:
print(err_msg)
def input_number(msg, err_msg=None):
while True:
try:
return float(input(msg))
except ValueError:
if err_msg is not None:
print(err_msg)
And to use it:
user_number = input_number("input a number: ", "that's not a number!")
Or, if you do not want an "error message":
user_number = input_number("input a number: ")