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import functools
import logging
import pprint
from itertools import chain
def format_call(args, kwargs):
args = (repr(a) for a in args)
kwargs = ("{!s}={!r}".format(*item) for item in kwargs.items())
return "({})".format(", ".join(chain(args, kwargs)))
def format_return(result, max_lines):
if isinstance(result, (list, tuple, set)):
return "({} with {} items)".format(type(result).__name__, len(result))
if result:
lines = pprint.pformat(result).split('\n')
extra = '\n...' if len(lines) > max_lines else ''
return '\n'.join(lines[:max_lines]) + extra
return result
class VerboseProxy:
"""Proxy all function calls to another class and log method name, arguments
and return values for each call.
"""
def __init__(self, obj_name, obj, log_name=None, max_lines=10):
self.obj_name = obj_name
self.obj = obj
self.max_lines = max_lines
self.log = logging.getLogger(log_name or __name__)
def __getattr__(self, name):
attr = getattr(self.obj, name)
if not callable(attr):
return attr
return functools.partial(self.proxy_callable, name)
def proxy_callable(self, call_name, *args, **kwargs):
self.log.info("%s %s <- %s",
self.obj_name,
call_name,
format_call(args, kwargs))
result = getattr(self.obj, call_name)(*args, **kwargs)
self.log.info("%s %s -> %s",
self.obj_name,
call_name,
format_return(result, self.max_lines))
return result
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