refactoring for easier use - FIX ADDED

[eqvis]

I wanted to have it easier to use, like this:

import patch
def entering(frame):
    print ">", frame.f_code.co_name
def leaving(frame):
    print "<", frame.f_code.co_name

def start():
     pass # insert your real content here!

patch.apply_patch(start, trace_call, trace_exit)
    start()

I added the following to patch.py

def before_call(fun):
    if not can_patch(fun):
        print "???: Calling builtin", fun
        return 1, 0
        
    res = patch_trace(fun)
    
    return res

before_call._pyspy_skip = 1

def patch_trace(fun):
    print "patch_trace", fun.__name__
    patch_calls(fun, before_call)

    if hasattr(fun, 'func_code'):
        if patch_trace._trace_call and hasattr(patch_trace._trace_call, "__call__"):
            patch_pre(fun, patch_trace._trace_call)
        if patch_trace._trace_return and hasattr(patch_trace._trace_return, "__call__"):
            patch_return(fun, patch_trace._trace_return)
    
#    if patch.patch_calls(fun, before_call):
    return PATCH_NOMORE, None

patch_trace._trace_call = None
patch_trace._trace_return = None

def apply_patch(fun_to_patch, callback_before=None, callback_after=None):
    patch_trace._trace_call = callback_before
    patch_trace._trace_return = callback_after
    
    patch_trace(fun_to_patch)