Editing Function object (section)

== In Python ==
In [[Python (programming language)|Python]], functions are first-class objects, just like strings, numbers, lists etc. This feature eliminates the need to write a function object in many cases. Any object with a <code>__call__()</code> method can be called using function-call syntax.

An example is this accumulator class (based on [[Paul Graham (computer programmer)|Paul Graham's]] study on programming language syntax and clarity):<ref>[http://www.paulgraham.com/accgen.html Accumulator Generator]</ref>

<syntaxhighlight lang="python">
class Accumulator:
    def __init__(self, n) -> None:
        self.n = n

    def __call__(self, x):
        self.n += x
        return self.n
</syntaxhighlight>

An example of this in use (using the interactive interpreter):

<syntaxhighlight lang="pycon">
>>> a = Accumulator(4)
>>> a(5)
9
>>> a(2)
11
>>> b = Accumulator(42)
>>> b(7)
49
</syntaxhighlight>

Since functions are objects, they can also be defined locally, given attributes, and  returned by other functions,<ref>[https://docs.python.org/3/reference/compound_stmts.html#function-definitions Python reference manual - Function definitions]</ref> as demonstrated in the following example:

<syntaxhighlight lang="python3">
def Accumulator(n):
    def inc(x):
        nonlocal n
        n += x
        return n
    return inc
</syntaxhighlight>