[Tutor] Handling binary file

[John Purser]

Julie,
 
I've had to work with some binary files with 3 byte data types.  They were
generated by an application coded in Business Basic.  Like you I grabbed it
as bytes and converted.  For clarity's sake I used powers of 2 instead of
hard coding the numbers.  2^8 makes it pretty obvious why you're multiplying
by 256 IMHO.  Look out for negative numbers though.  May not be applicable
to "number of seconds" but as a general rule watch for it.  Incidentally
when I had to read the same data with VBA I used the same technique to
reverse the byte order from Unix to Windows.  Worked just fine.
 
John Purser

  _____  

From: tutor-bounces at python.org [mailto:tutor-bounces at python.org] On Behalf
Of Julie Lai
Sent: Wednesday, August 24, 2005 18:20
To: tutor at python.org
Subject: [Tutor] Handling binary file


I have opened a file in binary mode. The 9th, 10th and 11th bytes contain
the time in seconds. In order to get this value in decimal I did the
following:   timeinsec = bytes[9] * 65536 + bytes[10] * 256 + bytes{11]
Would someone please advise if there is a better way to do this?   Thanks,
Julie. 

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