~~ function basis (a): ~ Parameters

进击 of python

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Function basis (a): Parameter

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== it clear that Austria, if you have not read the article front, then I suggest you do not look directly at the ==

== looked as a waste of time, does not make sense ==

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Well, then Python is part of the soul - function

In the course of history, we encounter complex problems, people always want to be able to simplify handling of the issue

Thus, the module ah, ah, what functions, including various algorithms on the heels of the

That function was originally how to come out of it?

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In the original ah, people encountered such a problem

# 报警装置，出现问题，发送问题到邮件

It is quite normal demand

How to write it (pseudo-code)

A = 故障
if A == "警报故障"
    打开QQ邮箱
    编辑警报故障邮件
    发送邮件
    关闭QQ邮箱
if A == "排水故障"
    打开QQ邮箱
    编辑排水故障邮件
    发送邮件
    关闭QQ邮箱
if A == "储水故障"
    打开QQ邮箱
    编辑储水故障邮件
    发送邮件
    关闭QQ邮箱
... ...

So people started to write, but soon it was discovered the problem

This code there are a lot of repeat statements

While it is possible when "CV Engineer", but humans still have to progress

So people think

These repeated, repeated use of the code statement on the "box", when used directly to box out

Thus, the function appeared!

This code can become so (do not ask why, look at the effect!):

def send_mail(x):
    打开QQ邮箱
    编辑x邮件
    发送邮件
    关闭QQ邮箱
    
A = 故障
send_mail(A)

Is not simply too much!

The reality finished, then start learning function journey!

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• grammar

  The syntax is a very important aspect to note the following:

  There must be a space behind def

  Function names follow the variable naming rules

  There are brackets behind the function name ()

  Brackets are behind a colon:

  def send_mail(): # 定义一个名为 send_mail 的函数

  Then the first line indent, write your code and write code as normal

  def send_mail():
      print("这是一个函数")

  Well, part of the function code is finished

  You can not perform is carried out, and why? Because you did not call

  How to call? Good question!

  In fact, we wrote this in front

  print()

  This is the Python comes with a function called print of

  That our custom function named send_mail how to call it?

  send_mail()

  I can understand that it (would not understand it again !!!)

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• parameter

  In fact, you should just have a question

  I have just introduced when the function definition, () it was empty, but inside is my example (x)

  What this does is x?

  It touches your knowledge to the blind

  Then talk about two concepts

  Arguments parameter

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  Arguments:

  You see people from the name, arguments

  What is the argument? Real parameters, or

  The real parameters

  for example:

  print("App")

  This App is my data to process, because I want to print this right

  That he is the parameter

  I know the contents of the parameter App Well it is not

  So this App is the real argument is the argument!

  Understand applause!

  This means that you listen to, as well as untrue parameters chant?

  ---

  Katachisan:

  Formal parameters, that is not true parameter

  Well, talking examples

  def send_mail(x):

  Come on, I was not trying to deal with this by x function?

  That this is not the x parameter?

  Then you tell me, what x is?

  1? 2? Cat? dog?

  I do not know it!

  That's parameter!

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• The default parameters

  Do you think you two kinds of parameters? ? Ausferrite want more juice!

  To really so simple, how can you call it soul?

  What is the default? Is that you do not change the default output something he

  For example, you select a city some App when it is not the default is Beijing?

  The default is that the default parameters

  For example

  def city(x="北京"):
      print(x)
  
  
  city()
  city("上海")

Why is this?

When you do not give this city function variables when the city function to use the default "Beijing" parameter passed to x; and when you give it a "Shanghai" parameter when you use your arguments to x

understand? Minato brother!

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• Positional parameters

  Positional parameters! Is a carrot a pit!

  def func(x, y, z):
      print("x:", x)
      print("y:", y)
      print("z:", z)
  
  
  func(1, 2, 3)
  

Order one by one, nothing to speak of this.

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• key parameter

  Look, it came out a parameter!
  The key parameters, in my opinion, should be called keyword arguments!

  Like a key-value dictionary mode

  def func(x, y, z):
      print("x:", x)
      print("y:", y)
      print("z:", z)
  
  
  func(y=1, z=2, x=3)

Simple is not? understand? It is not quite like key-value dictionary modes!

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• Non-fixed parameters

  The last Austrian, Shajiao non-fixed parameters?

  We still look at this function:

  def func(x, y, z):
      print("x:", x)
      print("y:", y)
      print("z:", z)

  I want to use this function, but I want to pass four parameters how to do? Direct write?

  func(1,2,3,4)

Some will complain! 4 Because you are not the parameter variables Next, you will complain ah!

Ever since, the clever "lazy" who would come up with this stuff

*args

Do not ask, would be finished by!

He is a container you extra positional arguments, in the manner of tuples stored up

def func(x, y, z,*args):
    print("x:", x)
    print("y:", y)
    print("z:", z)
    print("其他",*args)


func(1,2,3,4,5)

ok not? I do not understand?

Then again a stimulus!

** kwargs

What the hell? ? ? ? ? what is this? ? ? ? ? ?

This is a key parameter overflow storage container

def func(x, y, z, *args, **kwargs):
    print("x:", x)
    print("y:", y)
    print("z:", z)
    print("其他", *args)
    print("**kwargs:", kwargs)


func(1, 2, 3, 4, 5, key="hello")

It is stored in the form of the dictionary, ha ha ha ha ha ha ha ha ha ha! ! ! ! ! ! ! ! !

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