Assuming you mean that you are trying to conver the input to float,
you can do
myfloat = float(input("Enter a float: "))
However, do remember that this will return an expection if non-numbers and decimal points
are detected.
Here is a better version
import re
myfloat = float(re.sub("[^0-9.]","",input("Enter a float: ")))
It auto removes any nonnumeric and non decimal point characters.
pi = input("What's the value of pi? ")
pi = float(pi)