Programmer Didi 2022-06-23 18:00:33 阅读数:80
If the program is executed from top to bottom , The program will lack a lot of fun and transition , And it will lead to the programming boring , In this case , In order to achieve some effect , Need code to implement transition , This transition in the program is
Process control , from A You can go to B, You can also go to C.
In process control , You're going to learn
Relational operator And
Logical operators .
This blog has less content , Because the next article is going to talk about lists , That's a lot of knowledge , Let's learn a little bit of simple bedding first .
stay Python In fact, the relational operator is the concept of ratio size , So what we have to learn is greater than 、 Less than 、 Equal to the content of .
The specific relational operators are as follows ：
Greater than or equal to
Less than or equal to
be equal to
It's not equal to
If the conclusion is true , After the operation of the relational operator, it returns True, Instead of False.
Write a code test ：
a = 1 > 2 print(a) # False b = 2 > 1 print(b) # True
The left and right sides of a logical operator symbol can be variables , It can also be any value , The result return is a Boolean data type . Although this knowledge point is small , But very important .
Logical operators are in Python There is 3 individual , Namely
Expressions containing logical operators , The final result returned is also a Boolean value . Specific can refer to the following code ：
a = (1 > 2) and (2 > 1) print(a) # False b = 2 > 1 or 1 < 2 print(b) # True
The first formula uses
and Logical operators , On the left
1>2, The right side is
2>1. The final result of this formula is False.
There is an important point here as follows ：
andOperator , Need to be left and right for True, It turns out to be True, Otherwise, it's all for False.
orOperator , You need at least one for True, The final result is True.
notOperator signing is a negation operation , The original formula is False, After taking the reverse, it is True.
The above is the same as the relational operator , It doesn't make sense to just look at it , What is needed is practice in code and cases , In order to master .
Process control statements are also called branch statements , So when you look for information , Notice the name .
First you need to take a look if The syntax of the statement , If you have an impression .
if ( conditional ): Code block
The meaning is if
conditional The end result is True, perform
Code block Content , If
conditional The end result is False, Don't execute
Code block Content .
Here you have to learn Python How to indent , stay Python How to judge whether a code block is if The code block of the statement , It's dependence
Tab Or the key
4 A space To judge . Besides, don't leave out if There is a colon at the end of the line
: There is ~.
Let's take a look at the actual code , for example , Judge a person older than 18 year , The output code for adults is as follows ：
age = 20 if (age >= 18): print(" adults ")
In the above contents age = 20 , Be sure to be greater than 18, that age>=18 The result returned is True, Will execute if The code block inside the statement , And how to judge whether a piece of code belongs to if Inside the sentence , It is judged by indenting , See the picture for details ：
The red box above shows
Tab Indent . Indented is if Internal code blocks , At the bottom
if sentence irrelevant . Pay attention to the indented “ distance ” It has to be consistent , For example, the figure below is in Python Will make mistakes .
Indentation is Python An important basis for judging code blocks , from if Here you are first exposed to , It's going to be all over the back Python The whole learning career .
In the code just now if The following space can be omitted , Modify the code as follows ：
age = 20 if age >= 18: print(" adults ") print(" I belong to the above if sentence ") print(" I and if It doesn't matter ")
As a flow control statement , As long as there should be two possibilities , One is true , One is false , It can be called a process , Otherwise, it's done from top to bottom . So in addition to
if Beyond the sentence , also
else sentence , It can be understood that when the condition is true if The content of the code block in the statement , Execute when the condition is false else Statement code block content .
The syntax is as follows ：
if ( conditional ): if Code block for else: else Code block for
Complete a small example , When you are older than or equal to 18 Suggesting adulthood , Less than 18 It's suggestive of underage .
age = int(input(" Please enter your age ：")) if age >= 18: print(" adults ") print(" I belong to the above if sentence ") else: print(" A minor ") print(" I belong to the above else sentence ")
When there are multiple possibilities for process control , It needs to be used if ... elif ... else ... Statement , The syntax is as follows ：
if ( conditional ): if Code block elif ( conditional ): elif Code block else: else Code block
The most typical content is based on grades A、B、C... Grade , But we don't need this example , Find a fresh one , Calculation CSDN Author tax .
800 There's no tax paid inside 800 To 4000 The total amount paid minus 800 And then multiplied by the 20% 4000 To 20000 Of , Direct total amount of 16%
The code is as follows ：
money = int(input(" Please enter your income ：")) if money <= 800: print(" No tax ") elif money > 800 and money <=4000: print(" The amount of tax paid is ：",(money-800)*0.2) elif money>4000 and money<20000: print(" The amount of tax paid is ：", money * 0.16) else: print(" You earn too much , It's all buttoned up ")
Be sure to pay attention to , Indent 、 Indent 、 Indents are the same .
The content can be easily understood by the code , To put it bluntly if Statement set if sentence , As long as you can pay attention to indentation , You can go on and on , It's useless to say more , Imitate the following code , Try to run it .
money = int(input(" Please enter your income ：")) if money <= 800: print(" No tax ") if money > 0: print(" I've made money ") else: print(" Lost money ") elif money > 800 and money <=4000: print(" The amount of tax paid is ：",(money-800)*0.2) elif money>4000 and money<20000: print(" The amount of tax paid is ：", money * 0.16) else: if money > 100000000: print(" It's more than 100 million ") else: print(" Not making a hundred million ")
Relational and logical operators are often associated with if Statement with , Little knowledge , But very important .if The whole sentence is not difficult , But from this blog, you've been exposed to Python Is dependent on indentation for code segment control , This is a very small fulcrum , follow-up Python The style of grammar comes from it , Equally important , So this blog is all about the point .
The last bowl of poisonous chicken soup
Study hard Every day there is a new blow O(∩_∩)O ha-ha ~
版权声明：本文为[Programmer Didi]所创，转载请带上原文链接，感谢。 https://pythonmana.com/2021/12/202112312251561690.html