Writing decorator function in Python

Question

Apologies if it is repetitive but I am struggling to find a solution with this. I am trying to write a decorator function below.

  def search_func(sheetname):
    def insider(function):
        def wraper(*args, **kwargs):
            file = openpyxl.load_workbook("C:\\Users\khisr\OneDrive\Documents\TestPage.xlsx")
            currnet_sheet = file[sheetname]
            function(currnet_sheet)
        return wraper
    return insider         


@search_func('Passwords')
def Longin(self, currnet_sheet):
    Name = self.User_name.get() + str(self.Password.get())
    for i in range(1,current_sheet.max_row +1):
       for j in range(1,current_sheet.max_column+1):
           if current_sheet.cell(i,j).value == Name:

The function is called with a button;

self.Button = tk.Button(self.Main_frame, text='Enter', bg = 'green', command = self.Longin)

I get an error

"Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\ProgramData\Anaconda3\lib\tkinter\__init__.py", line 1705, in __call__
    return self.func(*args)
  File "C:/Users/khisr/OneDrive/Documents/PythonProjects/Dubai_Project/login.py", line 71, in wraper
    function(currnet_sheet)
TypeError: Longin() missing 1 required positional argument: 'currnet_sheet"

Any help or commend is much appreciated.

Cheers

Your decorator is fine . The issue is with whatever is calling the Longin method. Probably because tk.Button expects what you pass to be function not a method (methods require self). If you want Longin to be part of a class then try turning it into a @staticmethod. — Error - Syntactical Remorse
– Error - Syntactical Remorse, Commented Feb 13, 2020 at 14:05
Thanks, Can you elaborate on the @staticmethod? At the moment, the @search_func('Passwords') pass the 'Paswords' which is the page, I want the def search_func(sheetname) function to open. How can I pass the page name that needs to be opened using the @staticmethod? — user3064089
– user3064089, Commented Feb 13, 2020 at 14:09
Not the error but you probably want to return in your decorator: return function(currnet_sheet), otherwise if you decorate a method/function that returns something the decorator will consume it. — Error - Syntactical Remorse
– Error - Syntactical Remorse, Commented Feb 13, 2020 at 14:11
Sorry staticmethod wont work. You use self. Try using a lambda: self.Button = tk.Button(self.Main_frame, text='Enter', bg='green', command=lambda sheet: self.Longin(sheet)) — Error - Syntactical Remorse
– Error - Syntactical Remorse, Commented Feb 13, 2020 at 14:14

MisterMiyagi · Accepted Answer · 2020-02-13 14:30:05Z

1

Methods are bound to self when looked up on it. When decorating a method, the resulting decorated method is looked up on self, not the underlying method. You need to explicitly pass on the self parameter.

def search_func(sheetname):
  def insider(function):
      def wraper(self):  # the decorated method receives self...
          file = openpyxl.load_workbook("C:\\Users\khisr\OneDrive\Documents\TestPage.xlsx")
          currnet_sheet = file[sheetname]
          function(self, currnet_sheet)  # ...and should pass it on
      return wraper
  return insider

Note that if you want to support not just regular methods, you must (partially) replicate the descriptor protocol.

def search_func(sheetname):
  def insider(function):
      def wrapper(self):  # the decorated method receives self...
          file = openpyxl.load_workbook("C:\\Users\khisr\OneDrive\Documents\TestPage.xlsx")
          currnet_sheet = file[sheetname]
          function.__get__(self, type(self))(currnet_sheet)  # ...and should pass it on
      return wraper
  return insider

edited Feb 13, 2020 at 14:30

answered Feb 13, 2020 at 14:15

MisterMiyagi

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4 Comments

user3064089 Over a year ago

Thanks, I tried all the suggestions but I seem to get this error now. File "C:\ProgramData\Anaconda3\lib\tkinter_init_.py", line 1705, in call return self.func(*args) File "C:/Users/khisr/OneDrive/Documents/PythonProjects/Dubai_Project/login.py", line 70, in wraper function.__get__(self, type(self))(currnet_sheet) File "C:/Users/khisr/OneDrive/Documents/PythonProjects/Dubai_Project/login.py", line 78, in Longin for i in range(1,current_sheet.max_row +1): NameError: name 'current_sheet' is not defined

MisterMiyagi Over a year ago

@user3064089 That looks like another problem. It is not related to the code and question here.

user3064089 Over a year ago

It complains about that it doesn't find the "current_sheet' " but as you can see in the code that is passed to the function.

Jongware Over a year ago

@user3064089: you mean that currnet_sheet? Python is sensitive to typos in variable names. (Like, practically if not definitely all other programming languages.)

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