Python callable Built-in Function (original) (raw)

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Summary: in this tutorial, you’ll learn about Python callable objects and how to use the callable function to check if an object is callable.

Introduction to Python callables #

When you can call an object using the () operator, that object is callable:

object()Code language: Python (python)

For example, functions and methods are callable. In Python, many other objects are also callable.

A callable always returns a value.

To check if an object is callable, you can use the built-in function callable:

callable(object)Code language: Python (python)

The callable function accepts an object. It returns True if the object is callable. Otherwise, it returns False.

The following illustrates the various types of callable objects in Python.

1) built-in functions #

All built-in functions are callable. For example, print, len, even callable.

print(callable(print)) print(callable(len)) print(callable(callable))Code language: Python (python)

Output:

True True True Code language: PHP (php)

2) User-defined functions #

All user-defined functions created using def or lambda expressions are callable. For example:

`def add(a, b): return a + b

print(callable(add)) # True print(callable(lambda x: x*x)) # True`Code language: Python (python)

Output:

True TrueCode language: PHP (php)

3) built-in methods #

The built-in method such as a_str.upper, a_list.append are callable. For example:

str = 'Python Callable' print(callable(str.upper)) # TrueCode language: Python (python)

Output:

TrueCode language: PHP (php)

4) Classes #

All classes are callable. When you call a class, you get a new instance of the class. For example:

`class Counter: def init(self, start=1): self.count = start

def increase(self):
    self.count += 1

def value(self):
    return self.count`Code language: Python (python)

5) Methods #

Methods are functions bound to an object, therefore, they’re also callable. For example:

print(callable(Counter.increase)) # TrueCode language: Python (python)

Output:

TrueCode language: PHP (php)

6) Instances of a class #

If a class implements the __call__ method, all instances of the class are callable:

`class Counter: def init(self, start=1): self.count = start

def increase(self):
    self.count += 1

def value(self):
    return self.count

def __call__(self):
    self.increase()


counter = Counter()
counter()

print(callable(counter))  # True`Code language: Python (python)

Output:

TrueCode language: PHP (php)

Summary #

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