爲什麼我在這個腳本中得到一個NameError？

Question

我在做練習Non-Programmers Tutorial For Python2.6從Wikibooks。

我有這樣的腳本：

#!/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." 

這裏是殼發生了什麼：

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 

同樣的事情發生與C和R。

Answer 1

在Python 2中，input從用戶處獲取一個字符串並對其進行評估。所以當你輸入「S」時，它會嘗試評估它，尋找不存在的名字「S」。使用代替input。

是的，這太瘋狂了。它已在Python 3中修復，其中raw_input現在被命名爲input。