Python: Late Binding

Late binding, aka late evaluation is, good; it saves the machine time. Do not evaluate unless you need it.

What then, if a system evaluate the file before no one is ever sure that the file would be used or not?

Here is something that you can have a very strong opinion on. Would you want the system evaluating just by open()ing the file?

Look at the following code in Python. This is just opening up a log file.

import logging


LOGFORMAT = '[%(asctime)s] %(filename)s (%(lineno)d): %(message)s'

logging.basicConfig(
    filename='log/books.log',
    format=LOGFORMAT,
    datefmt='%Y-%m-%d %H:%M:%S',
    level=logging.DEBUG)

I am just setting the filename for logging. The file name could just be anything. <code>dummy.txt</code>, <code>&gt; null</code> thing. Right?

Then it took me a while decoding the error message that the Python is giving me.

"Server error! The server encountered an internal error and was unable to complete your request.
Error message: End of script output before headers: index.py
If you think this is a server error, please contact the webmaster."

This is a part of the web system, a CGI script.

It turns out, that Python demands a file. The file must be accessible, and writable. The permission must be set writable, before running this code.

Evaluating the validity of the file access before even writing anything out -- that was rather unexpected.

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