I have created a decorator to decorate all instance methods of a class. I have written following code to do so.
def debug(func):
msg = func.__name__
@wraps(func)
def wrapper(*args, **kwargs):
print(msg)
return func(*args, **kwargs)
return wrapper
# Decorator for all the methods in a class
def debugmethods(cls):
for key, val in vars(cls).items():
if callable(val):
setattr(cls, key, debug(val))
return cls
@debugmethods
class Spam:
def foo(self):
pass
def bar(self):
pass
Now I am trying to understand how this works, I mean when will this decoration happen and how can I check that?
a) It already happened?
b) When I access Spam class for the first time? For e.g.
for key, val in Spam.__dict__.items():
print(key, val)
c) When I instantiate Spam class for the first time? For e.g.
spam = Spam()
for key, val in Spam.__dict__.items():
print(key, val)
This is actually easily seen in action if you add a few print lines:
print('Deocrator is being defined')
def deco(cls):
print('Decorator is called')
cls.decorated = True
return cls
print('Foo is being defined')
@deco
class Foo:
print('Foo class attributes are being set')
def __init__(self):
print('Foo is being instantiated')
print('Foo class is being referenced in main script')
print(f'Foo is decorated: {Foo.decorated}')
print('Foo instance is being created in main script')
print(Foo())
Result:
Deocrator is being defined
Foo is being defined
Foo class attributes are being set
Decorator is called # <--- decoration happens immediately after definition of Foo
Foo class is being referenced in main script
Foo is decorated: True
Foo instance is being created in main script
Foo is being instantiated
<__main__.Foo object at 0x00789150>
In short, the answer is much like what @jonrsharpe said, it already happened. Just figure the visual would help.