sys_settrace_example_code.py

#!/usr/bin/env python
# encoding: utf-8

import sys

#
# Note: This code works on Python2 only!
#

ignore_functions = [
    'write',      # from print statement
    '_remove',    # from internal last cleanup
]


def trace_calls(frame, event, arg):
    if event not in ['call', 'return']:
        return
    if not ignore_functions:
        # on last cleanup, global variable may be already removed
        return

    co = frame.f_code
    func_name = co.co_name
    if func_name in ignore_functions:
        return

    func_line_no = frame.f_lineno
    local_variables = frame.f_locals
    if event == 'call':
        func_filename = co.co_filename
        caller = frame.f_back
        caller_line_no = caller.f_lineno
        caller_filename = caller.f_code.co_filename
        print 'Call to %s on line %s of %s from line %s of %s with arg (%s)' % \
            (func_name, func_line_no, func_filename,
             caller_line_no, caller_filename, local_variables)
        return trace_calls  # for return value can be monitored.
    elif event == 'return':
        print local_variables
        print 'return from [%s] line %s => %s' % (func_name, func_line_no, arg)
        return


class Hoge(object):
    def __init__(self):
        pass

    def d(self, args):
        return [args, args]


def b():
    def c(arg):
        print "in c()"
        hoge = Hoge()
        hoge.d(arg)
        return ['hoge', 'fuga', arg]
    print 'in b()'
    c(2)


def a():
    local_integers = [1, 2, 3]  # noqa
    print 'in a()'
    b()

sys.settrace(trace_calls)
a()

$ python sys_settrace_example_code.py 
Call to a on line 60 of sys_settrace_example_code.py from line 66 of sys_settrace_example_code.py with arg ({})
in a()
Call to b on line 50 of sys_settrace_example_code.py from line 63 of sys_settrace_example_code.py with arg ({})
in b()
Call to c on line 51 of sys_settrace_example_code.py from line 57 of sys_settrace_example_code.py with arg ({'arg': 2})
in c()
Call to __init__ on line 43 of sys_settrace_example_code.py from line 53 of sys_settrace_example_code.py with arg ({'self': <__main__.Hoge object at 0x7f03e8b78110>})
{'self': <__main__.Hoge object at 0x7f03e8b78110>}
return from [__init__] line 44 => None
Call to d on line 46 of sys_settrace_example_code.py from line 54 of sys_settrace_example_code.py with arg ({'self': <__main__.Hoge object at 0x7f03e8b78110>, 'args': 2})
{'self': <__main__.Hoge object at 0x7f03e8b78110>, 'args': 2}
return from [d] line 47 => [2, 2]
{'hoge': <__main__.Hoge object at 0x7f03e8b78110>, 'arg': 2}
return from [c] line 55 => ['hoge', 'fuga', 2]
{'c': <function c at 0x7f03e8b6e8c0>}
return from [b] line 57 => None
{'local_integers': [1, 2, 3]}
return from [a] line 63 => None