Python callable() Function

Python3 内置函数Python3 Built-in Functions

callable()Is a built-in function in Python used to check whether an object is callable.

In Python, functions, methods, classes, etc., are all callable objects.callable()It can help us check whether an object can be called before calling it, avoiding runtime errors.

Word Definition： callable 意为"可调用的"，表示对象是否可以像函数一样被调用。

Basic Syntax and Parameters

Syntax Format

callable(object)

Parameter Description

  • Parameter object：
    • Type: Any object
    • Description: The object to check.

Function Description

  • Return value: Returns a boolean valueTrueorFalse。
  • Note: Return True does not mean the call will definitely succeed, it just means the object is callable.

Examples

Example 1: Check Various Objects

Example

# Function
def my_func():
    pass

print(callable(my_func))  # Output: True

# Method
class MyClass:
    def my_method(self):
        pass

obj = MyClass()
print(callable(obj.my_method))  # Output: True

# Class (a class can be called to create instances)
print(callable(MyClass))  # Output: True

# Built-in function
print(callable(len))   # Output: True
print(callable(print))  # Output: True

# String (not callable)
print(callable("hello"))  # Output: False

# Number (not callable)
print(callable(123))  # Output: False

# Lambda expression
my_lambda = lambda x: x * 2
print(callable(my_lambda))  # Output: True

Expected output:

True
True
True
True
True
False
False
True

Code analysis:

  1. Functions, methods, classes, and lambda expressions are all callable.
  2. Basic types such as strings and numbers are not callable.

Example 2: Practical Application

Example

# Safely call a function
def safe_call(obj, *args, **kwargs):
    if callable(obj):
        return obj(*args, **kwargs)
    else:
        return f"{obj} is not callable"

# Test
def greet(name):
    return f"Hello, {name}!"

print(safe_call(greet, "Tom"))  # Output: Hello, Tom!
print(safe_call("not a function"))  # Output: not a function not callable

# Use in API design
class EventHandler:
    def __init__(self):
        self.handlers = {}

    def register(self, event, handler):
        if not callable(handler):
            raise TypeError("handler must be callable")
        self.handlers[event] = handler

    def trigger(self, event, *args):
        if event in self.handlers:
            return self.handlers[event](*args)

handler = EventHandler()
handler.register("click", lambda: "Handle click")
print(handler.trigger("click"))  # Output: Handle click

# Registering a non-callable object will raise an error
# handler.register("error", "not callable") # Raises TypeError

Expected output:

Hello, Tom!
not a function 不可调用
处理点击

callable()It is very useful when you need to dynamically call functions or verify callback functions.

Python3 内置函数Python3 Built-in Functions

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