strings and ints consistency - isinstance

[Sayth Renshaw]

To answer all the good replies.

I adapted a simple vector example from the Springer book practical primer on science with python.

Having solved the actual problem I thought checking with the user they had the correct entries or would like to ammend them would be a good addition. This leads to the question Y or N response which isn't hard but if someone accidentally types 4, then you get where I got stuck can't test an int for ValueError if you expect a string. 

This was my code

import sys

v0 = float(input("What velocity would you like? "))
g = float(input("What gravity would you like? "))
t = float(input("What time decimal would you like? "))

print("""
    We have the following inputs.
       v0 is %d
       g is  %d
       t is  %d
    Is this correct? [Y/n]
""" % (v0, g, t))
while True:
    try:
        answer = input("\t >> ").isalpha()
        print(v0 * t - 0.5 * g * t ** 2)
    except ValueError as err:
        print("Not a valid entry", err.args)
        sys.exit()
    finally:
            print("would you like another?")
            break

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When I look at this SO question it splits the votes half choose try except the other conditional logic, neither are wrong but which is the more obvious python way. https://stackoverflow.com/questions/2020598/in-python-how-should-i-test-if-a-variable-is-none-true-or-false

_______________________________________________________

I actually thought this would have resolved my issues and still returned error if ints entered however it still passes through.

answer = input("\t >> ")
if isinstance(answer, str) is True:
        print(v0 * t - 0.5 * g * t ** 2)
elif int(answer) is True:
    raise ValueError("Ints aren't valid input")
    sys.exit()
else:
    print("Ok please ammend your entries")

Thanks

Sayth