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)

翻译：argument：论点 

           intialize：初始化

           define a variable for called phrase：为被调用的短语定义一个变量