On Sun, Dec 30, 2012 at 8:18 PM, contro opinion <contropin...@gmail.com> wrote: > here is my haha class > class haha(object): > def theprint(self): > print "i am here" > >>>> haha().theprint() > i am here >>>> haha(object).theprint() > Traceback (most recent call last): > File "<stdin>", line 1, in <module> > TypeError: object.__new__() takes no parameters > > why haha(object).theprint() get wrong output?
The fact that `haha(object)` is textually part of the *declaration* `class haha(object):` has no bearing on how one instantiates an instance of the class `haha`. In the `class` statement, `haha` is being declared to be a subclass of class `object` (that's what it means for `object` to be in the parentheses after the class name in a `class` statement; the syntax is "class <classname>(<base classes>):"). In the first part of the *expression* `haha().theprint()`, you are using the function-call operator on the `haha` class itself, which has the effect of instantiating it; since you gave no arguments in the function call, haha's initializer (i.e. its __init__() method) was given no arguments. Since you didn't define an __init__() method for haha, haha inherited the default __init__() method from class `object`, which takes no arguments, so your call was fine and worked as expected. By contrast, in the first part of the *expression* `haha(object).theprint()`, you passed an argument (namely, `object`). Since __init__() wasn't expecting any arguments whatsoever, you therefore got an error. The parentheses in a `class` statement do NOT signify a function call; they are part of the syntax of the `class` statement itself. Cheers, Chris -- Note: I'm oversimplifying things a bit for the sake of understandability. -- http://mail.python.org/mailman/listinfo/python-list
