"NameError: name '' is not defined" after user input in Python [duplicate]

Question

I'm completely lost as to why this isn't working. Should work precisely, right?

UserName = input("Please enter your name: ")
print ("Hello Mr. " + UserName)
raw_input("<Press Enter to quit.>")

I get this exception:

Traceback (most recent call last):  
  File "Test1.py", line 1, in <module>
    UserName = input("Please enter your name: ")
  File "<string>", line 1, in <module>
NameError: name 'k' is not defined  

It says NameError 'k', because I wrote 'k' as the input during my tests. I've read that the print statement used to be without parenthesis but that has been deprecated right?

Answer 1

Do not use input() in 2.x. Use raw_input() instead. Always.

Answer 2

In Python 2.x, input() "evaluates" what is typed in. (see help(input)). Therefore, when you key in k, input() tries to find what k is. Because it is not defined, it raises the NameError exception.

Use raw_input() in Python 2.x. In 3.0x, input() is fixed.

If you really want to use input() (and this is really not advisable), then quote your k variable as follows:

>>> UserName = input("Please enter your name: ")
Please enter your name: "k"
>>> print UserName
k