byte compiled files

[Mark Robinson]

can anyone shed some light on the mysterious behaviour of my byte 
compiled files. I am currently working on a python script which analyses 
patterns in a DNA sequence. I have a function which checks a pattern (a 
substring of approx 6 chars) to ensure only valid charactors are 
present. When I first run this program it runs fine, but if I 
immediately rerun the program (i.e using the pre-byte compiled file) it 
finds all patterns non-valid. If I delete the .pyc file between runs 
this problem does not occur. Can anyone explain what is happening here 
to me and how to prevent it?

blobby