Conditionally import a Python module if it is available

I have been struggling with the issue of module availability in Python. While the “batteries included” nature of the standard library is great, there are occasionally times when I need to resort to a module that isn’t included with Python.

There are also times where I’m using modules whose status has changed. I expect that to happen more in the eventual transition to Python 2.6 and 3.0, because I’ve used modules that are being deprecated.

So I wondered how I could conditionally import a module if it was available, without stopping the flow of my scripts — and gracefully handle situations where it is missing. And here’s one basic answer: use a “try” block to catch the “ImportError” exception. For example, if I were concerned that DNSPython wasn’t going to be installed on my target system:

try:
import dns.resolver # Import DNSPython
dnspython_available = True
except ImportError:
dnspython_available = False

The “except ImportError” clause could specify a different module to load, or other workarounds entirely. You could map the namespaces in the “try” bock so the rest of your script doesn’t notice the change in module functions, if you have a way to work around the missing module. Perhaps, you could even try to obtain and install the module, at least for temporary use by your script.

Thanks to authors of the article Python modules – how do they work? for the assist. The information under heading 2.11, “Is my module available?” answered my question and has given me something to think about.