pyc file [Newbie Question]

Jim Aikin editor at
Tue Apr 3 08:44:41 CEST 2007

Just starting to learn Python and going through the Tutorial in the Help 
file. FWIW, I'm a hobbyist programmer -- not extremely knowledgeable, but 
not entirely clueless.

In 6.1.2 of the Tutorial, I find this: "The modification time of the version 
of used to create spam.pyc is recorded in spam.pyc, and the .pyc 
file is ignored if these don't match." Either I don't understand this, or it 
isn't correct.

Working through the tutorial, I created a file called in my text 
editor, and imported it into Idle. It worked as expected. I then edited the 
file and resaved it. I used del fibo, followed by import fibo.

My edits are not accessible in Idle. Python seems still to be importing the 
earlier version of fibo.pyc, even though the modification time of is 
now different. (I'm in Windows XP, if that makes a difference.)

I consistently get the error message "AttributeError: 'module' object has no 
attribute 'xyz'", even though I've just defined a new function xyz in and saved the file, then deleted and reimported.

One point of possible confusion here is in the line in the following 
paragraph of 6.1.2, "Whenever is successfully compiled...." My 
question is, is it compiled when being imported? I didn't spot any mention 
in the Tutorial of when or how a .py file might be (or would automatically 
be) compiled, so I'm assuming that it's automatically compiled while being 
imported. If this is a bad assumption, then maybe it's the root of my 
misunderstanding. Maybe I have to _do_ something to in order to 
create a new version of fibo.pyc.

Sorry to be so long-winded, but I want to be precise about this. Can anyone 
clarify for me what's happening here? Thanks!

--Jim Aikin

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