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Arevos · Dec 21st, 2005, 3:38 PM

I've been looking into generating Python bytecode from a Python program and this is what I've come up with:

def write_pyc(code, filename):
   "Write code to a PYC file"
   file = open(filename, 'wb')
   
   # PYC header specifying version and timestamp
   file.write(imp.get_magic())
   file.write(struct.pack('<l', time.time()))
   
   marshal.dump(code, file)

   file.close()


def compile_module(parse_tree, filename):
   "Compile a raw AST module"
   parse_tree.filename = filename
   return compiler.pycodegen.ModuleCodeGenerator(parse_tree).getCode()

The compile_module function is used to compile an AST (Abstract Syntax Tree) into a code object. The write_pyc function can write a compiled code object to a standard pyc file.

How do you create an AST? A good way to get a feel of Python ASTs is to get Python to generate them for you from existing files:

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print compiler.parseFile(py_filename)

You can also check out the table of AST node types that are listed here

Here's an AST I constructed myself:

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module = ast.Module(
   None,
   ast.Stmt(
      [ast.Printnl(
         [ast.CallFunc(
            ast.Name('pow'), [ast.Const(2), ast.Const(2)], None, None
         )],
         None
      )]
   )
)

This AST corresponds to the Python code: "print pow(2, 2)".

To compile this AST and write it to a file:

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filename = "four.pyc"
write_pyc(compile_module(module, filename), filename)

The bytecode can then be executed using:

(Toggle Plain Text)

python four.pyc

If all goes well, the number 4 should be printed to the screen.

Dec 21st, 2005, 3:38 PM	#1
Arevos Programming Guru Join Date: Aug 2005 Location: England Posts: 1,499 Rep Power: 5	Hacking the Python compiler I've been looking into generating Python bytecode from a Python program and this is what I've come up with: (Toggle Plain Text) def write_pyc(code, filename): "Write code to a PYC file" file = open(filename, 'wb') # PYC header specifying version and timestamp file.write(imp.get_magic()) file.write(struct.pack('<l', time.time())) marshal.dump(code, file) file.close() def compile_module(parse_tree, filename): "Compile a raw AST module" parse_tree.filename = filename return compiler.pycodegen.ModuleCodeGenerator(parse_tree).getCode() def write_pyc(code, filename): "Write code to a PYC file" file = open(filename, 'wb') # PYC header specifying version and timestamp file.write(imp.get_magic()) file.write(struct.pack('<l', time.time())) marshal.dump(code, file) file.close() def compile_module(parse_tree, filename): "Compile a raw AST module" parse_tree.filename = filename return compiler.pycodegen.ModuleCodeGenerator(parse_tree).getCode() The compile_module function is used to compile an AST (Abstract Syntax Tree) into a code object. The write_pyc function can write a compiled code object to a standard pyc file. How do you create an AST? A good way to get a feel of Python ASTs is to get Python to generate them for you from existing files: (Toggle Plain Text) print compiler.parseFile(py_filename) print compiler.parseFile(py_filename) You can also check out the table of AST node types that are listed here Here's an AST I constructed myself: (Toggle Plain Text) module = ast.Module( None, ast.Stmt( [ast.Printnl( [ast.CallFunc( ast.Name('pow'), [ast.Const(2), ast.Const(2)], None, None )], None )] ) ) module = ast.Module( None, ast.Stmt( [ast.Printnl( [ast.CallFunc( ast.Name('pow'), [ast.Const(2), ast.Const(2)], None, None )], None )] ) ) This AST corresponds to the Python code: "print pow(2, 2)". To compile this AST and write it to a file: (Toggle Plain Text) filename = "four.pyc" write_pyc(compile_module(module, filename), filename) filename = "four.pyc" write_pyc(compile_module(module, filename), filename) The bytecode can then be executed using: (Toggle Plain Text) python four.pyc python four.pyc If all goes well, the number 4 should be printed to the screen.