On Sun, 29 Jan 2012 14:01:01 -0500, Terry Reedy wrote: > On 1/29/2012 12:57 PM, HoneyMonster wrote: >> I am new to Python (Python 2.7 on Linux). Research indicates that: >> >> a) "Compiling" Python modules into intermediate bytecode marginally >> improves load time. > > The improvement is larger the larger the file. You may notice that .pyc > files are only created when a file is imported, not when it is run > directly. > >> b) The Python interpreter will use an already-prepared .pyc file if one >> exists in the same directory as the .py. >> >> That then, is presumably why for every .py file in my site-packages >> directory there is a corresponding .pyc file. > > In 3.2+, .pyc files are tucked away in a __pycache__ directory, with a > version indicator added to the names so one directory can be used with > more than one version of python. > >> Question 1: What then, are the .pyo files? I note that many of them are >> identical to the .pyc, but that some differ. > > They are created when imported into python started with -O (optimize). > That mainly deletes assertions and maybe something else. >> >> Question 2: What happens if the .py file is changed and the .pyc is >> thus made obsolete. Does the interpreter ignore the .pyc? If so, how >> does it know? By the timestamp? > > Yes. Yes.
Thanks, Terry and Cousin Stanley for the clear explanation and useful URL. -- http://mail.python.org/mailman/listinfo/python-list
