The mmap module provides support for a memory-mapped file object. This object behaves both like a file and a string and can be used in most places where an ordinary file or string is expected. Furthermore, the contents of a memory-mapped file are mutable. This means that modifications can be made using index-assignment and slice-assignment operators. Unless a private mapping of the file has been made, such changes directly alter the contents of the underlying file.
A memory-mapping file is created by the mmap() function, which is slightly different on UNIX and Windows.
mmap(fileno, length [, flags, [prot [,access]])
(UNIX) Returns an mmap object that maps length bytes from the file with an integer file descriptor, fileno. flags specifies ...