jupyter notebook for python （八）_letters,numbers,or undersc-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_21121571/article/details/103849428

本文介绍了Python中的函数参数和默认值。函数用于可重用的代码任务，可以带有或不带参数调用。参数是传递给函数的变量。通过在函数定义中设置默认参数，即使不提供实参，函数也能使用预设值。定义函数时，应使用以字母或下划线开头的名称，并遵循特定的语法结构，包括冒号和缩进。调用函数时，只需指定函数名后跟括号。print和len等内置函数接受参数，例如len函数接收一个对象并返回其类型。

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Functions Arguments & Parameters

Functions are used for code tasks that are intended to be reused

Python allows us to create User Defined Functions and provides many Built-in Functions such as print()

print() can be called using arguments (or without) and sends text to standard output, such as the console.
print() uses Parameters to define the variable Arguments that can be passed to the Function.
print() defines multiple string/numbers parameters which means we can send a long list of Arguments to print(), separated by commas.
print() can also be called directly with just its name and empty parentheses and it will return a blank line to standard output

（2）

`def some_function():`

use the def statement when creating a function

use a function name that starts with a letter or underscore (usually a lower-case letter)
function names can contain letters, numbers or underscores
parenthesis () follow the function name
a colon : follows the parenthesis
the code for the function is indented under the function definition (use 4 spaces for this course)

def some_function():
   #code the function tasks indented here

The end of the function is denoted by returning to no indentation

（3）Call a function by name

Call a simple function using the function name followed by parenthesis. For instance, calling print is
print()

（4） Functions that have Parameters

print() and type() are examples of built-in functions that have Parameters defined

type() has a parameter for a Python Object and sends back the type of the object

an Argument is a value given for a parameter when calling a function

type is called providing an Argument - in this case the string "Hello"
```
type("Hello")
```

Defining Function Parameters

Parameters are defined inside of the parenthesis as part of a function def statement
Parameters are typically copies of objects that are available for use in function code
```
def say_this(phrase):  
    print(phrase)
```

Function can have default Arguments

Default Arguments are used if no argument is supplied
Default arguments are assigned when creating the parameter list
```
def say_this(phrase = "Hi"):  
    print(phrase)
```