hello, I want to change n bytes of a binary file

[could ildg]

On 11/1/05, Fredrik Lundh <fredrik at pythonware.com> wrote:
>
> "could ildg" wrote:
>
> > I want to encrypt a very large birany file,
> > but if to change the whole file, it will take very long time,
> > so I just want to change n(n is an int) bytes of the file.
> > but when I turned to the file I/O of python, I found that file object
> can
> > only read and write strings,
> > so how can I do the binary stuff?
>
> 8-bit strings contain bytes.
>
> > I want a encrypt function like below:
> > def encrypt(filename,n):
>
> f = open(filename,"rb+")
>
> > a=f.read(n)
>
> b = encrypt(a)


^^^^^^^^Thank you~~,but where is the encrypt defined?

f.seek(0) # rewind
> f.write(b)
> f.close()
>
> </F>
>
>
>
> --
> http://mail.python.org/mailman/listinfo/python-list
>
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