waiting for file lock?

[s99999999s2003 at yahoo.com]

hi
i need to go into a directory to grab some files and do some
processing.
The thing is, i need to wait till the process that generates the files
in that directory to finish
before i can grab the files. eg if file A is being generated and has
not finished, my python script will not go into the directory.
how can i check that file A has actually finished?  thanks