Correct understanding of the reading and writing modes of Python files w +, a +, and r +

The difference between w + and r + is not hard to understand. There is also a +
+ Read and write at the same time, you can read and write at the same time, while writing at the same time, while reading and writing at the same time, without flush, can be measured using seek and tell.

Fp = open ("a.txt", "a +", 0) print 'open', fp. tell () x = fp. read () print 'open read () ', fp. tell () print xfp. write ("123456 \ n") print 'write 1-6 ', fp. tell () x = fp. read () print "first read \ n", xfp. seek (0) x = fp. read () print "second read \ n", x, fp. tell () fp. close ()

The first running result is:

Open 0 open read () 0 write 1-6 8 first readsecond read1234568

The result of the second run is

Open 0 open read () 8123456 write 1-6 16 first readsecond read12345612345616