equip 0.1

Python bytecode instrumentation framework

equip is a small library that helps with Python bytecode instrumentation. Its API is designed to be small and flexible to enable a wide range of possible instrumentations.

The instrumentation is designed around the injection of bytecode inside the bytecode of the program to be instrumented. However, the developer does not need to know anything about the Python bytecode.

The following example shows how to write a simple instrumentation tool that will print all method called in the program, along with its arguments:

import sys
import equip
from equip import Instrumentation, MethodVisitor, SimpleRewriter

BEFORE_CODE = """
print ">> START"
print "[CALL] {file_name}::{method_name}:{lineno}", {arguments}
print "<< END"
"""

class MethodInstr(MethodVisitor):
  def __init__(self):
    MethodVisitor.__init__(self)

  def visit(self, meth_decl):
    rewriter = SimpleRewriter(meth_decl)
    rewriter.insert_before(BEFORE_CODE)

instr_visitor = MethodInstr()
instr = Instrumentation(sys.argv[1])
if not instr.prepare_program():
  return
instr.apply(instr_visitor, rewrite=True)

This program requires the path to the program to instrument, and will compile the source to generate the bytecode to instrument. All bytecode will be loaded into its representation, and the MethodInstr visitor will be called on all method declarations.

When a change is required (i.e., the code actually needs to be instrumented), the Instrumentation will overwrite the pyc file.

Running the instrumented program afterwards does not require anything but executing it as you would usually do. If the injected code has external dependencies, you can simply modify the PYTHONPATH to point to the required modules.