Can't verify if a shape is a triangle

Question

from math import sqrt
a = raw_input("First length: ")
b = raw_input("Second length: ")
c = raw_input("Third length: ")
if a >0 and b >0 and c >0 and a + b > c and a + c > b and b + c > a :
    if a == b == c:
        print "Equilateral triangle."
    elif a == b and a != c and b != c:
        print "Isosceles triangle."
    elif (a==sqrt(b*b+c*c) or b==sqrt(a*a+c*c) or c==sqrt(a*a+b*b)):
        print "Right triangle."
    else:
        print "Simple triangle."
else:
    print "The shape is not a triangle."

When I insert "2", "2" and "2" everything is working well, but when i enter "3" , "4" and "5" I get: "The shape is not a triangle." . Can you help me find the problem? (I saw now that I could find the solution on another post, but I ... didn't know the problem)

`raw_input` returns a string, not numbers. You need `int(raw_input("First length: "))` or `float(raw_input("First length: "))`. it works for the same inputs because you are comparing strings that are the same. Once the string representation of those numbers changes, none of the `elif` clauses are true — roganjosh, Sep 29 '16 at 18:33
The `b != c` check is redundant; it is guaranteed to be true if the preceding two comparisons are true. — chepner, Sep 29 '16 at 18:35

score 0 · Accepted Answer · edited May 23 '17 at 12:33

0

In Python 2.7:

raw_input returns a str value. Either use input() OR typecast the raw_input() to int as:

int(raw_input("First length: "))

In Python 3

There is only input() performing the same action as raw_input() of Python 2.x, and raw_input don't exist in Python 3

Note: As per the Python 2.7 Document:

input('Something Something ...') is equivalent to eval(raw_input('Something Something ...')).

And we should not prefer using eval in the code due to security reasons. Read: Is using eval in Python a bad practice?

edited May 23 '17 at 12:33

Community

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answered Sep 29 '16 at 18:33

Moinuddin Quadri

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Don't recommend `input`. Python 3 got rid of it for a reason. – chepner Sep 29 '16 at 18:34
But user has mentioned tag as `python 2.7` – Moinuddin Quadri Sep 29 '16 at 18:35
@MoinuddinQuadri true, and `input` exists. However, it calls `eval()` on the input in Python 2.7, and `eval` is not safe. – roganjosh Sep 29 '16 at 18:36
Right; if it was Python 3, you wouldn't have a choice. `input` simply should not be used; use `raw_input` in its place and convert the value to the type you want, instead of letting Python guess and perhaps do more than you intended. – chepner Sep 29 '16 at 18:36
I agree with both of you on that. Added the Note on why input should not be used – Moinuddin Quadri Sep 29 '16 at 18:40

Can't verify if a shape is a triangle

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