How do you use the “def” keyword in Python?

1 year ago
Jackson Davis
2 minutes

In Python, the keyword def is used to define a function. A function is a reusable block of code that can be called anywhere in a program.

A typical function definition often includes the following parts:

def 函数名(参数1, 参数2, ...):
    # 函数体（代码块）
    ...
    return 返回值
  1. Definition: The keyword is used to indicate the start of a function declaration.
  2. Function name: Choose a suitable name for the function so that it can be called elsewhere.
  3. (Function can accept zero or more parameters, parameters are optional and can be added based on specific needs.)
  4. A colon signals the end of a function definition, with the following indented code block being the function body.
  5. Function body: a series of code statements contained within a function, used to implement the function’s functionality.
  6. Return is used to specify the return value of a function, which can optionally return one or multiple values. If no return value is specified, it defaults to None.

Here is a simple example which defines a function named “add” that calculates the sum of two numbers and returns the result.

def add(a, b):
    result = a + b
    return result

When using, you can call a function by its name combined with a list of arguments, and receive the return value.

result = add(3, 5)
print(result)  # 输出：8

Within a function body, any code logic can be executed, other functions can be called, and even other functions can be defined. The placement of a function’s definition can be either inside or outside of another function, depending on the code structure and requirements.

It is important to note that after a function is defined, it will not be executed immediately, but its internal code will only run when the function is called. Therefore, once a function is defined, it can be called multiple times at different points in the program.

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