Handling import errors when using doctest.

Question

Hi there,

every now and then when I code in Python, I have to do without certain third-party modules.

Eg. when I'm writing user authentication, it can be done in several ways and one of them is by using LDAP. However if the user does not want to use LDAP auth., he can choose a different option in a config file and in that case he should not have to have ldap module installed.

Generally I solve this by:

if config.foo: 
   import ldap_auth as auth
elif config.foo2:
   import other_auth as auth
...
auth.do_stuff(...)

and I import ldap module in ldap_auth module only. I personally find this quite nice, however, of course, doctests raise an ImportError when trying to execute ldap_auth.

Now, I know I could catch it by try-ing to import the ldap module in ldap_auth, but that just kinda messes up the nice looking code (the whole point of doing the whole "import ldap_auth as auth" bussiness was to avoid ImportErrors).

Is there any more elegant way to prevent doctests from raising ImportErrors when using this "pattern"?

Cheers,

Tom

Answer 1

The recommended way is

try:
    import foo as auth
except ImportError:
    import bar as auth

It avoids race conditions and I don't think it looks bad.