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17.5: The init method

  • Page ID
    40833
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    The init method (short for “initialization”) is a special method that gets invoked when an object is instantiated. Its full name is __init__ (two underscore characters, followed by init, and then two more underscores). An init method for the Time class might look like this:

    # inside class Time:
    
        def __init__(self, hour=0, minute=0, second=0):
            self.hour = hour
            self.minute = minute
            self.second = second
    

    It is common for the parameters of __init__ to have the same names as the attributes. The statement

            self.hour = hour
    

    stores the value of the parameter hour as an attribute of self.

    The parameters are optional, so if you call Time with no arguments, you get the default values.

    >>> time = Time()
    >>> time.print_time()
    00:00:00
    

    If you provide one argument, it overrides hour:

    >>> time = Time (9)
    >>> time.print_time()
    09:00:00
    

    If you provide two arguments, they override hour and minute.

    >>> time = Time(9, 45)
    >>> time.print_time()
    09:45:00
    

    And if you provide three arguments, they override all three default values.

    As an exercise, write an init method for the Point class that takes x and y as optional parameters and assigns them to the corresponding attributes.


    This page titled 17.5: The init method is shared under a CC BY-NC 3.0 license and was authored, remixed, and/or curated by Allen B. Downey (Green Tea Press) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.

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