Introduction to Python functions: usage and examples of dir function

Introduction to Python functions: Usage and examples of dir function

Python is an open source, high-level, interpreted programming language. It can be used to develop various types of applications, including web applications, desktop applications, games, etc. Python provides a large number of built-in functions and modules that can help programmers write efficient Python code quickly. Among them, the dir function is a very useful built-in function, which can help programmers view the properties and methods in an object, module or class.

Usage of the dir function

The dir function is one of the built-in functions of Python. Its function is to return a list of attributes and methods in an object, module or class. The syntax of this function is as follows:

dir([object])

Among them, the optional parameter object specifies the object to be checked. If object is omitted, the dir function returns a list of all properties and methods in the current scope. When object is specified, the dir function returns the list of properties and methods contained in the object.

The return value of the dir function is a list containing strings, where each string represents a property or method. The strings in the list are in no particular order.

Examples of dir function

The following are some specific examples of the dir function to help understand the usage of the dir function.

1. Return all properties and methods in the current scope

print(dir())

This line of code will print a list of all properties and methods in the current scope.

2. Return all properties and methods in the built-in module

import math
print(dir(math))

This line of code will print a list of all properties and methods in the math module.

3. Return all properties and methods in the user-defined class

class MyClass:
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def say_hello(self):
        print("Hello, my name is " + self.name + ", and I'm " + str(self.age) + " years old.")

obj = MyClass("Tom", 25)
print(dir(obj))

This line of code will print a list of all properties and methods in the MyClass instance. In this example, the attributes name and age and the method say_hello will be printed.

4. Return all properties and methods of Python built-in functions

print(dir(print))

This line of code will print a list of all properties and methods of the print function.

Summary

The dir function is a very useful built-in function. It helps programmers view the properties and methods in an object, module or class. When you want to view the properties and methods of an object or module, you can use the dir function. When using the dir function, you need to note that the return value is a list of strings in no specific order. At the same time, the dir function can also be used to return the properties and methods of Python's built-in functions.

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