When making a call to append in the python avro library does it stream results to file?

[web user]

writer = DataFileWriter(open(avro_filename, 'w'), DatumWriter(),
                      schema)

for r in xrange(100000000000)
writer.append({
   'id': i})

write.close()

Will the writer in this case stream data to a file?

Regards,

WU