Question

I’m doing exercises form Non-Programmers Tutorial For Python2.6 from Wikibooks.

I have this script:

#!/usr/bin/env python
#-*- coding:utf-8 -*-

print("Program to calculate the area of square, rectangle and circle.")

def areaOfSquare():
    side = input("What is the length of one side of the square? ")
    area = side ** 2
    return area

def areaOfRectangle():
    width = input("What is the width of the rectangle? ")
    height = input("What is the height of the rectangle? ")
    area = 2*width+2*height
    return area

def areaOfCircle():
    radius = input("What is the radius of the circle? ")
    area = 3.14 * radius ** 2
    return area

geometry = input("What do you wan to calculate the area of? [S/C/R] ")

str(geometry)

if geometry == "S":
    areaOfSquare()
elif geometry == "R":
    areaOfRectangle()
elif geometry == "C":
    areaOfCircle()
else:
    print "Press S for square, C for circle and R for rectangle."

Here is what happened in shell:

prompt$ python script.py 
Program to calculate the area of square, rectangle and circle.
What do you wan to calculate the area of? [S/C/R] S
Traceback (most recent call last):
  File "allarea.py", line 22, in <module>
    geometry = input("What do you wan to calculate the area of? [S/C/R]")
  File "<string>", line 1, in <module>
NameError: name 'S' is not defined

Same thing happens with C and R.

Answer 1

In Python 2, input takes a string from the user, and evaluates it. So when you enter “S”, it tries to evaluate it, looking for the name “S”, which doesn’t exist.

Use raw_input instead of input.

Yes, this was crazy. It’s fixed in Python 3, where raw_input is now named input.