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    <p>No, it isn't necessary.</p> <p>For example.</p> <pre><code>class A(object): def f(): print 'foo' </code></pre> <p>And you can of course use it, in this manner:</p> <pre><code>a = A() a.f() </code></pre> <p>In fact you can even define a class in this manner.</p> <pre><code>class A: pass </code></pre> <p>However, defining <code>__init__</code> is a common practice because instances of a class usually store some sort of state informtion or data and the methods of the class offer a way to manipulate or do something with that state information or data. <code>__init__</code> allows us to initialize this state information or data while creating an instance of the class. </p> <p>Here is a complete example.</p> <pre><code>class BankAccount(object): def __init__(self, deposit): self.amount = deposit def withdraw(self, amount): self.amount -= amount def deposit(self, amount): self.amount += amount def balance(self): return self.amount # Let me create an instance of 'BankAccount' class with the initial # balance as $2000. myAccount = BankAccount(2000) # Let me check if the balance is right. print myAccount.balance() # Let me deposit my salary myAccount.deposit(10000) # Let me withdraw some money to buy dinner. myAccount.withdraw(15) # What's the balance left? print myAccount.balance() </code></pre> <p>An instance of the class is always passed as the first argument to a method of the class. For example if there is <code>class A</code> and you have an instance <code>a = A()</code>, whenever you call <code>a.foo(x, y)</code>, <code>Python</code> calls <code>foo(a, x, y)</code> of <code>class A</code> automatically. (Note the first argument.) By convention, we name this first argument as <code>self</code>.</p>
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    1. POIs it necessary to include __init__ as the first function every time in a class in Python?
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    1. USSusam Pal
    1. USSusam Pal
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    1. COcan u please explain in detail about the use of __init__???
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    2. COITYM `a = A()`, although `a = A` also works but does something different.
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      1. USAlok Singhal
    3. COAlok, Thanks. Fixed it.
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