TypeError: coercing to Unicode: need string or buffer

You're trying to open each file twice! First you do:

infile=open('110331_HS1A_1_rtTA.result','r')

and then you pass infile (which is a file object) to the open function again:

with open (infile, mode='r', buffering=-1)

open is of course expecting its first argument to be a file name, not an opened file!

Open the file once only and you should be fine.

For the less specific case (not just the code in the question - since this is one of the first results in Google for this generic error message. This error also occurs when running certain os command with None argument.

For example:

os.path.exists(arg)  
os.stat(arg)

Will raise this exception when arg is None.