What is "marshal data"?

Michael Hudson mwh at python.net
Thu Nov 15 20:24:28 CET 2001

Cliff Wells <logiplexsoftware at earthlink.net> writes:

> On Thursday 15 November 2001 10:28, Soren Ragsdale wrote:
> > Possible sources of the problem: "uh.py" is imported from MANY
> > programs on our network.  It's being imported by Linux and Irix
> > machines running 1.5.2 and 2.1.1 versions of Python.  Could this be
> As mentioned in another thread, the bytecode between python versions is not 
> backward compatible, so you may be trying to execute 2.1.1 bytecode on a 
> 1.5.2 interpreter and that may be causing the problem.

Shouldn't be.  The first four bytes of a .pyc file are a
version-specific magic number, meant to stop this happening.

Executing the wrong bytecode would cause SystemErrors or core dumps,
not ValueErrors complaining about marshal data -- the marshal module
does little checking of its input, as it's only there to speed things


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