Using boolean operators in an if statement

Question

I'm a beginner in coding, and I'm trying to create a quadratic equation calculator using python.

while True:
    print("""
        Welcome to DJIGURDA Supreme Quadratic Calculator
        Please enter three values in the form of /'ax^2 + bx +c/'. """)
    a = input("a (first constant)")
    b = input("b (second constant)")
    c = input("c (third constant)")

    if not a.isalpha and not b.isalpha and not c.isalpha:
        d = (float(b)**2) - (4 * float(a) * float(c))
        print(d)
        if d >= 0:
            x_1 = (float(-b) + (d**0.5)) / (2*float(a))
            x_2 = (float(-b) - (d**0.5)) / (2*float(a))
            print("The first variable is equal to %s./n The second variable is equal to %s")[str(x_1), str(x_2)]
        else: 
            print("No real roots.")
    else:
        print("Please enter numerical values.")

This code keeps returning "Please enter numerical values." Why is the code not making it past the first "if" statement?

Brackets. You need each boolean if section to have brackets () around it. — Tim
– Tim, Commented Jul 11, 2016 at 18:59
try if (not a.isalpha()) and (not b.isalpha()) and (not c.isalpha()): — Tim
– Tim, Commented Jul 11, 2016 at 19:00
ps: you do not need brackets around the if tests (not binds stronger than and) — thebjorn
– thebjorn, Commented Jul 11, 2016 at 19:03

Moses Koledoye · Accepted Answer · 2016-07-11 19:01:23Z

8

You're not calling those methods:

c.isalpha()
#        ^^

Note that a method or function in Python has a truthy value:

>>> bool(''.isalpha)
True

So not a.isalpha (and others) will always evaluate to False and the condition will never pass

answered Jul 11, 2016 at 19:01

Moses Koledoye

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1 Comment

Vladimir K. Bobyr Over a year ago

That's exactly what I'm trying to do, since I need numerical input.

doodle911 · Accepted Answer · 2016-07-12 13:44:17Z

0

You must put brackets around the a.isalpha - like this a.isalpha () this calls the method whereas before it didn't. You must do it for b and c as well

UPDATE

Sorry I just realised someone has answered this like I have way before me, please don't accept my answer and accept theirs!

answered Jul 12, 2016 at 13:44

doodle911

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