Trying to both append and read from a file handle

appender.py

#!/usr/bin/env python3
f = open('somefile.txt','a+')
while True:
  text = input('Say something silly ')
  if text:
    f.write(text)
    print('CONTENT:',f.read())
  else:
    f.close()
    break

The issue is that write and read are figting over the same pointer:

#!/usr/bin/env python3
f = open('somefile.txt','a+')
while True:
  text = input('Say something silly ')
  if text:
    loc = f.write(text)
    f.seek(0)
    print('CONTENT:',f.read())
    f.seek(loc)
  else:
    f.close()
    break

The updated version still isn't quite right. It will put the cursor loc bytes into the file, which is potentially backing it up in the file, if somefile.txt already had contents in it. write() returns the number of bytes written, not the absolute position in the file. If you wish to leave the cursor at the end of the file, you can drop f.seek(loc) entirely.

To see the problem I'm talking about try doing the following (untested, written in the textbox) code:

rm somefile.txt
for x in `seq 1 10`; do date >> somefile.txt ; done

#!/usr/bin/env python3
f = open('somefile.txt','a+')
while True:
  text = input('Say something silly ')
  if text:
    loc = f.write(text)
    f.seek(0)
    print('CONTENT:',f.read())
    f.seek(loc)
    f.write('==== Corrupt the text! ====')
    f.seek(0)
    print('CONTENT AFTER SECOND WRITE:',f.read())
  else:
    f.close()
    break