> Like Victor says, that opens him up to race conditions. Slim chance, it's no more possible than it happening in the time try/except takes to recover an alternative procedure.
with open('in_file') as in_file, open('out_file', 'ab') as outfile_file: if os.path.getsize('out_file'): print('file not empty') else: #write header print('file was empty') And if that's still not acceptable (you did say new) than open the out_file 'r+' an seek and read to check for a header. But if your file is not new and lacks a header, then what? jlc -- https://mail.python.org/mailman/listinfo/python-list