Logged In: YES 
user_id=31435

Which version of Python are you talking about?  Also, please 
give a concrete example so we don't have to guess at what 
you mean.  Here's mine:

"""
import mmap

f = open('in.txt', 'rb')
m = mmap.mmap(f.fileno(), 0, 
access=mmap.ACCESS_READ)
f.close()

print `m[:]`
m.resize(5)
"""
The m.resizes() attempt yields a TypeError, "mmap can't 
resize a readonly or copy-on-write memory map".  I tried this 
under current CVS, and under 2.2.1, on Win2K.