python - Making sure input is a float -

this might noob question, me this? need make sure input strictly float. current code returns error, no matter type of input.

    pricepercandy = float(input('please enter price per candy (2 decimal places): '))     if pricepercandy.isalpha() or pricepercandy.isalnum():         print("please enter price 2 decimal places.")         pricepercandy = float(input('please enter price per candy (2 decimal places): ')) 

you can write simple function read input until float value enterd user

>>> def readfloat(): ...     while true: ...             try: ...                     value = float(input("enter value ")) ...                     return value ...             except valueerror: ...                     print "please enter price 2 decimal places" 

test

>>> readfloat() enter value "asdf" please enter price 2 decimal places enter value "qwer" please enter price 2 decimal places enter value 1.2 1.2