如何在Python 2中从键盘获取用户输入？

Question

I wrote a function in Python which prompts the user to give two numbers and adds them. It also prompts the user to enter a city and prints it. For some reason, when I run it in a shell, I get "name is not defined" after I enter the city.

def func_add(num1, num2):
   a = input("your city")
   print a
   return num1 + num2 

Answer 1

If you're on Python 2, you need to use raw_input :

def func_add(num1, num2):

   a = raw_input("your city")
   print a
   return num1 + num2 

input causes whatever you type to be evaluated as a Python expression, so you end up with

a = whatever_you_typed

So if there isn't a variable named whatever_you_typed you'll get a NameError .

With raw_input it just saves whatever you type in a string, so you end up with

a = 'whatever_you_typed'

which points a at that string, which is what you want.

Answer 2

input()

executes (actually, evaluates) the expression like it was a code snippet, looking for an object with the name you typed, you should use

raw_input()

This is a security hazard, and since Python 3.x, input() behaves like raw_input(), which has been removed.

Answer 3

you want to use raw_input . input is like eval

Answer 4

You want to use raw_input() instead. input() expects Python, which then gets eval ed.

Answer 5

You want raw_input , not input .

input(...)
    input([prompt]) -> value

    Equivalent to eval(raw_input(prompt)).

As opposed to...

raw_input(...)
    raw_input([prompt]) -> string

    Read a string from standard input.  The trailing newline is stripped.
    If the user hits EOF (Unix: Ctl-D, Windows: Ctl-Z+Return), raise EOFError.
    On Unix, GNU readline is used if enabled.  The prompt string, if given,
    is printed without a trailing newline before reading.

Answer 6

In Python 2.x, input asks for a Python expression (like num1 + 2 ) which is then evaluated. You want raw_input which allows one to ask for arbitrary strings.