Alexander Belopolsky wrote:
> 
> Alexander Belopolsky <belopolsky@users.sourceforge.net> added the comment:
> 
>> To avoid the wasted memory and import time, it's better to use:
>>
>> try:
>>    from _cmodule import *
>> except ImportError:
>>    from _pymodule import *
>>
> 
> .. also this makes it harder to prototype things in Python or have mixed Python/C modules.  The goal is to use Python implementation unless native implementation exists on per function/class basis.  The syntax above makes it all or nothing.

Why ?

You can have the Python parts that are used by both implementation
defined in the datetime.py module.

Alternatively, you could write:

try:
    # Use the faster C version
    from _module import *
except ImportError:
    # Use Python
    class datetime:
        ...

I find that rather ugly, though.