mmap_write_slice_Errno2IOError.py

#1/usr/bin/env python

# this is from The Python
# Standard Library by example
# ISBN13: 9780321767349

import mmap
import shutil
import contextlib

# Copy the example file
shutil.copyfile('lorem.txt', 'lorem_copy.txt')

word = 'consectetuer'
reversed = word[::-1]
print 'Looking for    :', word
print 'Replacing with :', reversed

with open('lorem_copy.text', 'r+') as f:
    with contextlib.closing(mmap.mmap(f.fileno(), 0)) as m:
        print 'Before:'
        print m.readline().rstrip()
        m.seek(0)  # rewind

        loc = m.find(word)
        m[loc:loc + len(word)] = reversed
        m.flush()

        m.seek(0)  # rewind
        print 'After :'
        print m.readline().rstrip()

        f.seek(0)  # rewind
        print 'File  :'
        print f.readline().rstrip()

"""
$ python mmap_write_slice.py
Looking for    : consectetuer
Replacing with : reutetcesnoc
Traceback (most recent call last):
File "mmap_write_slice.py", line 19, in <module>
with open('lorem_copy.text', 'r+') as f:
IOError: [Errno 2] No such file or directory: 'lorem_copy.text'
"""
# This is wierd, checked over and over for typos
# I can see that the file exists
# Tried using absolute path names and got the same error