How to decorate a method inside a class?

user_26143 0
Viewed 42871

I am attempting to decorate a method inside a class but python is throwing an error. My class looks like this:

from pageutils import formatHeader

class myPage(object):
   def __init__(self):
      self.PageName = ''

   def createPage(self):
      pageHeader = self.createHeader()

   @formatHeader   #<----- decorator
   def createHeader(self):
       return "Page Header ",self.PageName

if __name__=="__main__":
   page = myPage()
   page.PageName = 'My Page'
   page.createPage()

pageutils.py:

def formatHeader(fn):
   def wrapped():
       return '<div class="page_header">'+fn()+'</div>'
   return wrapped

Python throws the following error

self.createHeader()
TypeError: wrapped() takes no arguments (1 given)

Where am I goofing?

decorator python
3 Answers

You can also decorate the method at runtime, but not at define time. This could be useful in the case where you don't have access to or don't want to edit the source code, for example.


In [1]: class Toy():
   ...:     def __init__(self):
   ...:         return
   ...:     def shout(self, s):
   ...:         print(s)
   ...:

In [2]: def decor(fn):
   ...:     def wrapper(*args):
   ...:         print("I'm decorated")
   ...:         return fn(*args)
   ...:     return wrapper
   ...:


In [4]:

In [4]: a=Toy()

In [5]: a.shout('sa')
sa

In [6]: a.shout=decor(a.shout)

In [7]: a.shout('sa')
I'm decorated
sa
user_21067530
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