On Sun, 12 Mar 2006 22:01:46 -0500, John Salerno wrote: > Erik Max Francis wrote: > >> You can use the struct module for converting fundamental types to a >> portable string representation for writing to binary files. > > But if it's a string, why not just use a text file? What does a binary > file do that a text file doesn't, aside from not converting the end of > line characters?
Nothing. It is all bytes under the hood. People generally consider a file to be "text" if it only includes bytes 32 through 126, plus a few control characters like 9 (tab) and 10 (newline). Other applications don't care what bytes are included. Python is (mostly) like that: you can deal with any bytes you collect from any file. Other than this informal difference between text an binary, the major difference comes about when you read lines from a text file. Each operating system has a line separator: Unix/BSD/Linux systems use newline (char 10), classic Macintosh used to use carriage return (char 12) and DOS/Windows uses a two-byte carriage return + newline. When writing lines to a file, Python does not automatically append the line marker, so you need to do so yourself. But some other languages do -- I believe C++ is one of those languages. So C++ needs to know whether you are writing in text mode so it can append that end-of-line maker, or binary mode so it doesn't. Since Python doesn't modify the line you write to the file, it doesn't care whether you are writing in text or binary mode, it is all the same. Operating systems such as Unix and Linux don't distinguish between binary and text mode, the results are the same. I'm told that Windows does distinguish between the two, although I couldn't tell you how they differ. -- Steven. -- http://mail.python.org/mailman/listinfo/python-list
