Python dynamically add decorator to class' methods by decorating class
Unless there is a definite reason to use a class as a decorator, I think it is usually easier to use functions to define decorators.
Here is one way to create a class decorator trace
, which decorates all methods of a class with the log
decorator:
import inspect
def log(func):
def wrapped(*args, **kwargs):
try:
print("Entering: [%s] with parameters %s" % (func.__name__, args))
try:
return func(*args, **kwargs)
except Exception as e:
print('Exception in %s : %s' % (func.__name__, e))
finally:
print("Exiting: [%s]" % func.__name__)
return wrapped
def trace(cls):
# https://stackoverflow.com/a/17019983/190597 (jamylak)
for name, m in inspect.getmembers(cls, lambda x: inspect.isfunction(x) or inspect.ismethod(x)):
setattr(cls, name, log(m))
return cls
@trace
class X(object):
def first_x_method(self):
print('doing first_x_method stuff...')
def second_x_method(self):
print('doing second_x_method stuff...')
x = X()
x.first_x_method()
x.second_x_method()
yields:
Entering: [first_x_method] with parameters (<__main__.X object at 0x7f19e6ae2e80>,)
doing first_x_method stuff...
Exiting: [first_x_method]
Entering: [second_x_method] with parameters (<__main__.X object at 0x7f19e6ae2e80>,)
doing second_x_method stuff...
Exiting: [second_x_method]
Here's a version of the trace
decorator implemented as a class which allows for the other use case asked for: passing in the function to decorate all member functions of the decorated class with.
import inspect
def log(func):
def wrapped(*args, **kwargs):
try:
print "Entering: [%s] with parameters %s" % (func.__name__, args)
try:
return func(*args, **kwargs)
except Exception, e:
print 'Exception in %s : %s' % (func.__name__, e)
finally:
print "Exiting: [%s]" % func.__name__
return wrapped
class trace(object):
def __init__(self, f):
self.f = f
def __call__(self, cls):
for name, m in inspect.getmembers(cls, inspect.ismethod):
setattr(cls, name, self.f(m))
return cls
@trace(log)
class X(object):
def first_x_method(self):
print 'doing first_x_method stuff...'
def second_x_method(self):
print 'doing second_x_method stuff...'
x = X()
x.first_x_method()
x.second_x_method()