python - input() error - NameError: name '...' is not defined -

i getting error when try run simple python script:

input_variable = input ("enter name: ") print ("your name is" + input_variable) 

lets type in "dude", error getting is:

line 1, in <module> input_variable = input ("enter name: ") file "<string>", line 1, in <module> nameerror: name 'dude' not defined 

i running mac os x 10.9.1 , using python launcher app came install of python 3.3 run script.

edit: realized somehow running these scripts 2.7. guess real question how run scripts version 3.3? thought if dragged , dropped scripts on top of python launcher app inside python 3.3 folder in applications folder launch scripts using 3.3. guess method still launches scripts 2.7. how use 3.3?

tl;dr

input function in python 2.7, evaluates whatever enter, python expression. if want read strings, use raw_input function in python 2.7, not evaluate read strings.

if using python 3.x, raw_input has been renamed input. quoting python 3.0 release notes,

raw_input() renamed input(). is, new input() function reads line sys.stdin , returns trailing newline stripped. raises eoferror if input terminated prematurely. old behavior of input(), use eval(input())

---

in python 2.7, there 2 functions can used accept user inputs. 1 input , other 1 raw_input. can think of relation between them follows

input = eval(raw_input) 

consider following piece of code understand better

>>> dude = "thefourtheye" >>> input_variable = input("enter name: ") enter name: dude >>> input_variable 'thefourtheye' 

input accepts string user , evaluates string in current python context. when type dude input, finds dude bound value thefourtheye , result of evaluation becomes thefourtheye , gets assigned input_variable.

if enter else not there in current python context, fail nameerror.

>>> input("enter name: ") enter name: dummy traceback (most recent call last):   file "<input>", line 1, in <module>   file "<string>", line 1, in <module> nameerror: name 'dummy' not defined 

security considerations python 2.7's input:

since whatever user types evaluated, imposes security issues well. example, if have loaded os module in program import os, , user types in

os.remove("/etc/hosts") 

this evaluated function call expression python , executed. if executing python elevated privileges, /etc/hosts file deleted. see, how dangerous be?

to demonstrate this, let's try execute input function again.

>>> dude = "thefourtheye" >>> input("enter name: ") enter name: input("enter name again: ") enter name again: dude 

now, when input("enter name: ") executed, waits user input , user input valid python function invocation , invoked. why seeing enter name again: prompt again.

so, better off raw_input function, this

input_variable = raw_input("enter name: ") 

if need convert result other type, can use appropriate functions convert string returned raw_input. example, read inputs integers, use int function, shown in this answer.

in python 3.x, there 1 function user inputs , called input, equivalent python 2.7's raw_input.