Numeric type conversions

[John Dann]

I'm new to Python and can't readily find the appropriate function for
the following situation:

I'm reading in a byte stream from a serial port (which I've got
working OK with pyserial) and which contains numeric data in a packed
binary format. Much of the data content occurs as integers encoded as
2 consecutive bytes, ie a 2-byte integer.

I'm guess that there should be a function available whereby I can say
something like:

My2ByteInt = ConvertToInt(ByteStream[12:13])

to take a random example of the 2 bytes occurring at positions 12 and
13 in the byte stream.

Can anyone point me in the right direction towards a suitable function
please?

NB I don't know without further checking exactly how the bytes are
encoded, but I'm just transcribing some code across from a Windows
VB.Net program and these same bytes could be read straight into a
standard 2-byte signed short int, so I can be confident that it's a
fairly standard Windows-compatible encoding.