python codes runs using idle but fails on command line?

Question

Hi all,

I am learning python, i have written a script per an example in the book I am reading where it imports the urllib library. This works fine when i run it from IDLE but if i go to the folder when the file is and run "python test.py" i get an error where it tells me that

    Traceback (most recent call last):
  File "test.py", line 1, in ?
    import urllib.request
ImportError: No module named request

I verified that I am using python 3.1.2, any suggestions or ideas why this fails on the command line? Thanks in advance.

my code:

import urllib.request
import time

price = 99.99
while price > 1.01:
    time.sleep(3)
    page = urllib.request.urlopen("http://www.beans-r-us.biz/prices.html")
    text = page.read().decode("utf8")
    where = text.find('>$')
    start_of_price = where + 2
    end_of_price = start_of_price + 4
    price = float(text[start_of_price:end_of_price])

print ("Buy!")

Answer 1

Well, the error is saying it can't find the library, so there is something different between the environments.

Here's a tutorial on python modules that could help.

Have a look at the PYTHONPATH environment variable:

 $ echo $PYTHONPATH

at least on a UNIX box. (Don't recall for Windows, honestly.)

Have a look also at Python's built in path with the line

 print sys.path

Odds on are that PYTHONPATH differs between the command line and IDLE environments.

Answer 2

urllib.request was introduced with Python 3. It is very possible that when you run the code from the command line, you are using an older, Python 2.x binary.

Type python --version on the command line to see which python is being used.

Edit in response to Drewdin's comment

Running the Python 3.1.2 installer for Mac OSX, I see this:

NOTE: This package will by default not update your shell profile and will also not install files in /usr/local. Double-click Update Shell Profile at any time to make 3.1.2 the default Python.

The installer puts the applications in "Python 3.1" in your Applications folder, and the underlying machinery in /Library/Frameworks/Python.framework. It can optionally place links to the command-line tools in /usr/local as well, by default you have to add the "bin" directory inside the framework to you shell's search path.

So depending on how you installed it, you may already have links placed in /usr/local/bin, which will be in your path. If you chose this option at install time, all you should have to do is type python3 or python3.1 in your shell to get the updated version.

Otherwise, either double click that "Update Shell Profile", or add this to your path:

export PATH=$PATH:/Library/Frameworks/Python.framework/Versions/3.1/bin

By default, Python 3.x does not make the python command alias in Unix/Linux environments because it could possibly interfere with system processes/commands dependent on the default-installed python.

Answer 3

Either you do from urllib import request,

or you specify it during the call

import urllib
urlib.request (...)

Answer 4

Drewdin, when you type 'python' in your Terminal command line, it will display the version that it's running. If it's not 3.1, which is when urllib.request was introduced, try python3.1 test.py

Also, try import urllib instead of import urllib.request