On Mon, May 27, 2013 at 4:01 PM, Jim Mooney <cybervigila...@gmail.com> wrote: > I was looking at the bytecode doc page as a break from the Lutz book, > since I like Assembler-type code due to its total non-ambiguity, but > the page doesn't say much. Is there a doc somewhere that corresponds > some of the bytecode to Python source? I thought rot_1, 2, 3, and 4 > looked useful, but it would take awhile to disassemble random programs > to see what source they come from.
Are you referring to the documentation of the dis module? http://docs.python.org/2/library/dis AFAIK, that's all the documentation there is. Heed the warning in bold that bytecode is an implementation detail of the target virtual machine. For example, Jython creates a .class file containing JVM bytecode, and its code objects don't even have a co_code attribute... I once manually instantiated a CPython 2.x code object to create a very simple function with a default argument. Here was my first and only attempt, FWIW: from opcode import opmap from types import FunctionType, CodeType from inspect import CO_OPTIMIZED, CO_NEWLOCALS, CO_NOFREE OP = type('OP', (), opmap) def foo1(x='spam'): print x foo2 = FunctionType( CodeType( # func_code 1, # co_argcount 1, # co_nlocals 1, # co_stacksize CO_OPTIMIZED | # co_flags CO_NEWLOCALS | CO_NOFREE, str(bytearray([ # co_code OP.LOAD_FAST, 0, 0, # stack.push(fastlocals[0]) # x is fastlocals[0] OP.PRINT_ITEM, # print stack.pop() OP.PRINT_NEWLINE, OP.LOAD_CONST, 0, 0, # stack.push(co_consts[0]) # co_consts[0] is None OP.RETURN_VALUE, # return stack.pop() ])), (None,), # co_consts (), # co_names ('x',), # co_varnames __file__, # co_filename 'foo2', # co_name 10, # co_firstlineno '\x00\x01', # co_lnotab, # see: Objects/lnotab_notes.txt (), # co_freevars (), # co_cellvars ), globals(), # func_globals 'foo2', # func_name ('spam',), # func_defaults None, # func_closure ) For example: >>> foo2() spam >>> foo2('eggs') eggs There's an assembler package on PyPI that does this for real, if this sort of thing interests you: https://pypi.python.org/pypi/BytecodeAssembler As to the VM's ROT operations, I'm not sure what you mean by seeing "what source they come from". They simply manipulate the top 2, 3, or 4 items on the frame's stack: ROT_TWO() Swaps the two top-most stack items. ROT_THREE() Lifts second and third stack item one position up, moves top down to position three. ROT_FOUR() Lifts second, third and forth stack item one position up, moves top down to position four. _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
