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Python exit handlers (atexit)

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atextit — it is a python module that contains two functions register () and unregister () . The main role of this module is to perform cleanup after the interpreter exits. Registered functions are automatically executed when the interpreter terminates. Whenever a program os.exit () with a signal not handled by Python, when os.exit () or a fatal internal Python error is encountered, the functions registered through this module are are not executed.

  • register (): The Register function takes a function as an argument to be executed when the interpreter exits. If several functions are passed as arguments, for example (fun1 (), fun2 () ..), then the execution will be in reverse order (… fun2 (), fun1 ()). Execution takes place on a last-come-first basis; first came out ”(LIFO). 

    Syntax: atexit.register (fun, * args, ** kwargs)

    Parameters: First the function name is mentioned and then any arguments for that function is passed. The parameters are separated using ’,’.

    Return: This function returns the called fun and hence the calling can be traced.

    Note. This function can also be used as a decorator.

    # Example 1:

     
    # Python demo
    # atexit module

     

     

    import atexit

     

    names = [ ’Geeks’ , ’for’ , < / code> ’Geeks’ ]

      

    def hello (name):

      print (name)

      

    for name in names:

     

    # Using register ()

      atexit.register (hello, name)

    Output:

     Geeks for Geeks 

    # Example 2: Using case as a decorator

    # Python program for demonstration
    # atexit module

      

      

    import atexit

     
    # Using register () as a decorator

    @ atexit . register

    def goodbye ():

    print ( "GoodBye." )

    Output:

     GoodBye. 
  • unregister (): The unregister () function removes the specified pleasure from functions defined in the program. This ensures that the fun is not triggered when the translator is done. 

    Syntax: atexit.unregister (fun)

    Parameters: The function may or may not contain any parameter ... If any present then the fun name is to be specified.

    Return: No return.

    Example:

    # Python program for demonstration
    # atexit module

     

     

    import atexit

      

    names = [ ’Geeks’ , ’for’ , ’Geeks’ ]

      

    def hello (name): < / p>

    print (name)

     

    for name in names:

     

    # Using unregister ()

    atexit.unregister (hello) 

    Output:

     No Output 

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