Question

I’m trying to catch any exceptions that happen when you cannot load a module.
The current results are that the “except” block does not get executed.

import sys 
def loadModule(module):
   try: 
      import module
   except: 
      print """ 
      Cannot load %s
      For this script you will need: 
         cx_Oracle:  http://cx-oracle.sourceforge.net/
         pycrypto:   https://www.dlitz.net/software/pycrypto/
         paramiko:   http://www.lag.net/paramiko/
       """ % module
      sys.exit(1)

loadModule(cx_Oracle)

Error:

Traceback (most recent call last):
  File "./temp_script.py", line 16, in <module>
    loadModule(cx_Oracle)
NameError: name 'cx_Oracle' is not defined

Answer 1

loadModule(cx_Oracle)

What do you think you are passing to this function? There is nothing named cx_Oracle in the code so far. That’s why you are getting a NameError. You aren’t even getting into the function.

 import module

You can’t pass variables to import, it interprets what you put in as the literal name of the module

In this case, I question that you even need a function. Just move the try/except to the module level and import cx_Oracle directly.

Just because I was curious, here is a way you can make a reusable exception-catching import function. I’m not sure when/how it would be useful, but here it is:

from contextlib import contextmanager
import sys

@contextmanager
def safe_import(name):
    try:
        yield
    except:
        print 'Failed to import ' + name
        sys.exit(1)

with safe_import('cuckoo'):
    import cuckoo