Attempting to read open file a second time gets no data

Question

fin = open(\'/abc/xyz/test.txt\', \'a+\')

def lst():
  return fin.read().splitlines()

print lst()

def foo(in):
  print lst()
  fin.write(str(len(lst()) + in)
  fi         


        

Answer 1

Once you've called read() once fin has been read.

If you want to read() it again (having discarded the contents on the first attempt), you'll need to re-open() or seek() the start of the file.

I suggest you do this in lst(), or, better still, store the contents returned by lst()

Aside from that...

fin.write(str(len(lst()) + in)

It's not clear what you're trying to do here, but you'd be better off using a stored return value from lst() and not using in as a variable name, since it's a reserved keyword.

Something like:

lines = lst()
# [...]
number_of_lines = len(lines)
fin.write(str(number_of_lines) + some_other_str)