When Method Overloading Doesn\'t Work in Python?

Method Overloading in Python

In Python, method overloading is the ability to define multiple methods with the same name but different parameters. However, this can lead to some unexpected behavior.

Example 1:

<code class="python">class A:
    def stackoverflow(self):    
        print ('first method')
    def stackoverflow(self, i):
        print ('second method', i)</code>

If you call the method with an argument, the second method will be invoked:

<code class="python">ob=A()
ob.stackoverflow(2)
# Output: second method 2</code>

But if you call it without an argument, Python will raise an error:

<code class="python">ob=A()
ob.stackoverflow()
# Output: TypeError: stackoverflow() takes exactly 2 arguments (1 given)</code>

This is because Python considers the first method as having no arguments, not one default argument.

Solution:

To solve this issue, you can use default parameter values:

<code class="python">class A:
    def stackoverflow(self, i='some_default_value'):
        print('only method')</code>

Now, both calls will work:

<code class="python">ob=A()
ob.stackoverflow(2)
# Output: only method
ob.stackoverflow()
# Output: only method</code>

Advanced Overloading with Single Dispatch

Python 3.4 introduced single dispatch generic functions, which allow you to define specific behaviors for different argument types:

<code class="python">from functools import singledispatch

@singledispatch
def fun(arg, verbose=False):
    if verbose:
        print(&quot;Let me just say,&quot;, end=&quot; &quot;)
    print(arg)

@fun.register(int)
def _(arg, verbose=False):
    if verbose:
        print(&quot;Strength in numbers, eh?&quot;, end=&quot; &quot;)
    print(arg)

@fun.register(list)
def _(arg, verbose=False):
    if verbose:
        print(&quot;Enumerate this:&quot;)
    for i, elem in enumerate(arg):
        print(i, elem)</code>

This allows you to call fun with different argument types and get the appropriate behavior:

<code class="python">fun(42)
# Output: Strength in numbers, eh? 42
fun([1, 2, 3])
# Output: Enumerate this:
# 0 1
# 1 2
# 2 3</code>

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