How do I use raw_input in Python 3
import sys print(sys.platform) print(2**100) raw_input()
I am using Python 3.1 and can't get the
raw_input to "freeze" the dos pop-up. The book I'm reading is for Python 2.5 and I'm using Python 3.1
What should I do to fix this?
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This works in Python 3.x and 2.x:
# Fix Python 2.x. try: input = raw_input except NameError: pass print("Hi " + input("Say something: "))
As others have indicated, the
raw_input function has been renamed to
input in Python 3.0, and you really would be better served by a more up-to-date book, but I want to point out that there are better ways to see the output of your script.
From your description, I think you're using Windows, you've saved a
.py file and then you're double-clicking on it to run it. The terminal window that pops up closes as soon as your program ends, so you can't see what the result of your program was. To solve this, your book recommends adding a
input statement to wait until the user presses enter. However, as you've seen, if something goes wrong, such as an error in your program, that statement won't be executed and the window will close without you being able to see what went wrong. You might find it easier to use a command-prompt or IDLE.
Use a command-prompt
When you're looking at the folder window that contains your Python program, hold down shift and right-click anywhere in the white background area of the window. The menu that pops up should contain an entry "Open command window here". (I think this works on Windows Vista and Windows 7.) This will open a command-prompt window that looks something like this:
Microsoft Windows [Version 6.1.7601] Copyright (c) 2009 Microsoft Corporation. All rights reserved. C:\Users\Weeble\My Python Program>_
To run your program, type the following (substituting your script name):
...and press enter. (If you get an error that "python" is not a recognized command, see http://showmedo.com/videotutorials/video?name=960000&fromSeriesID=96 ) When your program finishes running, whether it completes successfully or not, the window will remain open and the command-prompt will appear again for you to type another command. If you want to run your program again, you can press the up arrow to recall the previous command you entered and press enter to run it again, rather than having to type out the file name every time.
IDLE is a simple program editor that comes installed with Python. Among other features it can run your programs in a window. Right-click on your
.py file and choose "Edit in IDLE". When your program appears in the editor, press F5 or choose "Run module" from the "Run" menu. Your program will run in a window that stays open after your program ends, and in which you can enter Python commands to run immediately.
Timmerman's solution works great when running the code, but if you don't want to get
Undefined name errors when using pyflakes or a similar linter you could use the following instead:
try: import __builtin__ input = getattr(__builtin__, 'raw_input') except (ImportError, AttributeError): pass
Here's a piece of code I put in my scripts that I wan't to run in py2/3-agnostic environment:
# Thank you, python2-3 team, for making such a fantastic mess with # input/raw_input :-) real_raw_input = vars(__builtins__).get('raw_input',input)
Now you can use real_raw_input. It's quite expensive but short and readable. Using raw input is usually time expensive (waiting for input), so it's not important.
In theory, you can even assign raw_input instead of real_raw_input but there might be modules that check existence of raw_input and behave accordingly. It's better stay on the safe side.