In short, each line represents a row in a database ... Now you know how to write to a file in Python regardless of the type of file! Of course, some files are going to contain more complex ...

The problem I've noticed is that if I append the file with each of the 100k runs (one at a time), it can happen that two threads try to save to the file at the same time and some row(s) end up empty.

So I have a program in Python for use ... 0') by os.write() and nothing is written past that. This becomes apparent when reading from /dev/zero and writing to a file -- the file never grows ...