Check input is a float

''' calculate basic laws of motion '''
import random
import sys
import os

def isfloat(value):
    ''' check argument string contains a valid float or integer, return True or False accordingly '''
    if value.isnumeric(): return True
    try:
        float(value)
    except ValueError:
        return False
    else:
        return True

def getfloat(prompt):
    ''' display argument prompt, keep going until valid numeric input entered, return float cast of input '''
    while True:
        user_entry = input(prompt)
        if isfloat(user_entry):
            return float(user_entry)
        else:
            print('That is not a valid input. Try again.')

print("Laws of motion")
print("Calculate if v=v0+at")

v0 = getfloat('Enter v0: ')
a = 9.8
t = getfloat("Enter t: ")
v = v0 + a * t
print('v = ', v)