Source code for boltons.debugutils

# -*- coding: utf-8 -*-

# Copyright (c) 2013, Mahmoud Hashemi
#
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"""
A small set of utilities useful for debugging misbehaving
applications. Currently this focuses on ways to use :mod:`pdb`, the
built-in Python debugger.
"""

import sys
import time

try:
    basestring
    from repr import Repr
except NameError:
    basestring = (str, bytes)  # py3
    from reprlib import Repr

try:
    from typeutils import make_sentinel
    _UNSET = make_sentinel(var_name='_UNSET')
except ImportError:
    _UNSET = object()

__all__ = ['pdb_on_signal', 'pdb_on_exception', 'wrap_trace']


[docs]def pdb_on_signal(signalnum=None): """Installs a signal handler for *signalnum*, which defaults to ``SIGINT``, or keyboard interrupt/ctrl-c. This signal handler launches a :mod:`pdb` breakpoint. Results vary in concurrent systems, but this technique can be useful for debugging infinite loops, or easily getting into deep call stacks. Args: signalnum (int): The signal number of the signal to handle with pdb. Defaults to :mod:`signal.SIGINT`, see :mod:`signal` for more information. """ import pdb import signal if not signalnum: signalnum = signal.SIGINT old_handler = signal.getsignal(signalnum) def pdb_int_handler(sig, frame): signal.signal(signalnum, old_handler) pdb.set_trace() pdb_on_signal(signalnum) # use 'u' to find your code and 'h' for help signal.signal(signalnum, pdb_int_handler) return
[docs]def pdb_on_exception(limit=100): """Installs a handler which, instead of exiting, attaches a post-mortem pdb console whenever an unhandled exception is encountered. Args: limit (int): the max number of stack frames to display when printing the traceback A similar effect can be achieved from the command-line using the following command:: python -m pdb your_code.py But ``pdb_on_exception`` allows you to do this conditionally and within your application. To restore default behavior, just do:: sys.excepthook = sys.__excepthook__ """ import pdb import sys import traceback def pdb_excepthook(exc_type, exc_val, exc_tb): traceback.print_tb(exc_tb, limit=limit) pdb.post_mortem(exc_tb) sys.excepthook = pdb_excepthook return
_repr_obj = Repr() _repr_obj.maxstring = 50 _repr_obj.maxother = 50 brief_repr = _repr_obj.repr # events: call, return, get, set, del, raise def trace_print_hook(event, label, obj, attr_name, args=(), kwargs={}, result=_UNSET): fargs = (event.ljust(6), time.time(), label.rjust(10), obj.__class__.__name__, attr_name) if event == 'get': tmpl = '%s %s - %s - %s.%s -> %s' fargs += (brief_repr(result),) elif event == 'set': tmpl = '%s %s - %s - %s.%s = %s' fargs += (brief_repr(args[0]),) elif event == 'del': tmpl = '%s %s - %s - %s.%s' else: # call/return/raise tmpl = '%s %s - %s - %s.%s(%s)' fargs += (', '.join([brief_repr(a) for a in args]),) if kwargs: tmpl = '%s %s - %s - %s.%s(%s, %s)' fargs += (', '.join(['%s=%s' % (k, brief_repr(v)) for k, v in kwargs.items()]),) if result is not _UNSET: tmpl += ' -> %s' fargs += (brief_repr(result),) print(tmpl % fargs) return
[docs]def wrap_trace(obj, hook=trace_print_hook, which=None, events=None, label=None): """Monitor an object for interactions. Whenever code calls a method, gets an attribute, or sets an attribute, an event is called. By default the trace output is printed, but a custom tracing *hook* can be passed. Args: obj (object): New- or old-style object to be traced. Built-in objects like lists and dicts also supported. hook (callable): A function called once for every event. See below for details. which (str): One or more attribute names to trace, or a function accepting attribute name and value, and returning True/False. events (str): One or more kinds of events to call *hook* on. Expected values are ``['get', 'set', 'del', 'call', 'raise', 'return']``. Defaults to all events. label (str): A name to associate with the traced object Defaults to hexadecimal memory address, similar to repr. The object returned is not the same object as the one passed in. It will not pass identity checks. However, it will pass :func:`isinstance` checks, as it is a new instance of a new subtype of the object passed. """ # other actions: pdb.set_trace, print, aggregate, aggregate_return # (like aggregate but with the return value) # TODO: test classmethod/staticmethod/property # TODO: wrap __dict__ for old-style classes? if isinstance(which, basestring): which_func = lambda attr_name, attr_val: attr_name == which elif callable(getattr(which, '__contains__', None)): which_func = lambda attr_name, attr_val: attr_name in which elif which is None or callable(which): which_func = which else: raise TypeError('expected attr name(s) or callable, not: %r' % which) label = label or hex(id(obj)) if isinstance(events, basestring): events = [events] do_get = not events or 'get' in events do_set = not events or 'set' in events do_del = not events or 'del' in events do_call = not events or 'call' in events do_raise = not events or 'raise' in events do_return = not events or 'return' in events def wrap_method(attr_name, func, _hook=hook, _label=label): def wrapped(*a, **kw): a = a[1:] if do_call: hook(event='call', label=_label, obj=obj, attr_name=attr_name, args=a, kwargs=kw) if do_raise: try: ret = func(*a, **kw) except: if not hook(event='raise', label=_label, obj=obj, attr_name=attr_name, args=a, kwargs=kw, result=sys.exc_info()): raise else: ret = func(*a, **kw) if do_return: hook(event='return', label=_label, obj=obj, attr_name=attr_name, args=a, kwargs=kw, result=ret) return ret wrapped.__name__ = func.__name__ wrapped.__doc__ = func.__doc__ try: wrapped.__module__ = func.__module__ except Exception: pass try: if func.__dict__: wrapped.__dict__.update(func.__dict__) except Exception: pass return wrapped def __getattribute__(self, attr_name): ret = type(obj).__getattribute__(obj, attr_name) if callable(ret): # wrap any bound methods ret = type(obj).__getattribute__(self, attr_name) if do_get: hook('get', label, obj, attr_name, (), {}, result=ret) return ret def __setattr__(self, attr_name, value): type(obj).__setattr__(obj, attr_name, value) if do_set: hook('set', label, obj, attr_name, (value,), {}) return def __delattr__(self, attr_name): type(obj).__delattr__(obj, attr_name) if do_del: hook('del', label, obj, attr_name, (), {}) return attrs = {} for attr_name in dir(obj): try: attr_val = getattr(obj, attr_name) except Exception: continue if not callable(attr_val) or attr_name in ('__new__',): continue elif which_func and not which_func(attr_name, attr_val): continue if attr_name == '__getattribute__': wrapped_method = __getattribute__ elif attr_name == '__setattr__': wrapped_method = __setattr__ elif attr_name == '__delattr__': wrapped_method = __delattr__ else: wrapped_method = wrap_method(attr_name, attr_val) attrs[attr_name] = wrapped_method cls_name = obj.__class__.__name__ if cls_name == cls_name.lower(): type_name = 'traced_' + cls_name else: type_name = 'Traced' + cls_name if hasattr(obj, '__mro__'): bases = (obj.__class__,) else: # need new-style class for even basic wrapping of callables to # work. getattribute won't work for old-style classes of course. bases = (obj.__class__, object) trace_type = type(type_name, bases, attrs) for cls in trace_type.__mro__: try: return cls.__new__(trace_type) except Exception: pass raise TypeError('unable to wrap_trace %r instance %r' % (obj.__class__, obj))
if __name__ == '__main__': obj = wrap_trace({}) obj['hi'] = 'hello' obj.fail import pdb;pdb.set_trace()