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This article introduces the knowledge of "how to use Python language". In the operation of practical cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Answer this question first

Why do you want to learn programming languages? Before reading any further, please think carefully and write down the reasons on the paper. One day I asked my students the same question. They gave me these answers:

"I want to find a good job in a famous software company, so I need to learn a programming language."

"learning a programming language allows me to learn some advanced technologies, such as artificial intelligence and machine learning."

Most of the answers are similar to the above, and the main reason for learning a programming language is to find a job or apply it to advanced technology. The world has been teaching you in the wrong way that you will get what you learn. Any tutorials you read or watch about programming languages will start with real-life languages.

If there is a solution in the real world, what is the use of learning it?

Now you have to remember one thing-you shouldn't learn to program for any purpose. In fact, no one can teach you programming. Because "programming is not a subject, but a basic ability of the human brain."

So, before you continue to read, forget all the reasons for learning the language and devote yourself to it. I'm not sure if you will eventually become a software developer. However, I am sure you will realize that programming is a natural language.

II. Python programming language

There are more than 700 programming languages to choose from in the world, and only some of them are noticed. I began to learn programming in 2015. I was first exposed to the C language, and I am now in awe of C.

However, when I studied Python in 2019, I fell in love with it at first sight, and I still do. I don't know why, maybe it's because of its concise syntax, or because its code is highly readable. Anyway, something attracts me and keeps me passionate about it. I'm sure you'll like the language, too, and the way it deals with problems.

Guido van Rossum, creator of Python, said: the joy of writing Python code lies in concise and readable classes that represent a large number of actions with only a small amount of clear code, rather than a flood of trivial code.

If you want to pick a language to start your programming career, you can consider python because its code is very simple and readable. We will use language to convey some information to others, and programming is just a language to communicate with computers. If you need a programming language that is almost the same as a human language, then python is right for you.

When you talk to your friends, you don't need to add a semicolon at the end, and you don't need to mention the type of data you're talking about. This is human language. Even as a programming language, Python has the same features.

After reading the following content, you are equivalent to the beginning of Python, let's go!

How to print information in Python

A program should be able to deliver something after compilation. Usually, a program is a set of instructions given to a computer. After receiving the instruction, the computer understands the instruction and then responds to us by outputting (Output) values. The output value will be printed on the console (console) window, you can use the interpreter or IDE for programming.

In order to make it easier to understand, the first five parts will be explained by imaginary concepts. Imagine you are sitting alone in the park. Let me explain this first scene. When you are sitting on a park bench, you see an old friend sitting next to you, and now you are saying to that person, "Hi, I'm Felix, remember me?" The first shot ends here.

In the above scenario, what you say is equivalent to the output. We can try to print the same content with the help of python. In python, if you want to print statements in the console, you must use the print () command.

This is the code to be printed, that is, if you ask that person:

Print ("Hi. I am Felix. Do youremember me?")

You can now think of it as an instruction of Python. It will print the following output in the console.

Hi. I am Felix. Do you rememberme?

The same output can be obtained in four different ways:

Print ("Hi. I am Felix. Do youremember me?") Or print ('Hi. I am Felix. Do you remember me?') Or print (''Hi. I am Felix. Do you remember me?''') Or print ("" Hi. I am Felix. Do you remember me? ")

Fourth, get user input

Now come back to the park. Unfortunately, your old friend can't understand what you're saying. So he said, "excuse me, what's your name?" Now, look at two expressions in this case. The first one is just a statement. However, the second one is to ask you for information. You can type this statement in the console using the input () command. The difference between print () and input () is that input requires something to be typed after the statement is executed. The dialogue is as follows:

Print ("Hi. I am Felix. Do youremember me?") Input ("Sorry. What is your Name?")

Output.

Hi. I am Felix. Do you rememberme? Sorry. What is your Name?

At the end of this output, you can enter your name in the console.

Fifth, the concept of using variable names

He recognized you in seconds after telling him your name. Then he said, "Hi! Felix, how have you been?"

Now please understand this sentence clearly. He used your name correctly in this expression. How do you do that? Because, after getting your name, his brain stores your name with certain tags, such as your name Felix. With such a memory, he can use your name anywhere.

As mentioned above, programming is a natural language, it is just another form of expression of human instinct. Computers also have a memory for storing large amounts of information. Now, (whenever you use an input statement) you say your name to the console, and the input given in the console is stored in memory. After that, the name must be retrieved from memory.

To do this, we provide a unique name for the input by assigning values. The name used to reference input is called a variable. Simply put, the name of the memory location is Variable.

Print ("Hi. I am Felix. Do youremember me?") Name = input ("Sorry. What is your Name?")

Look at the modified code, which executes the same as the previous code. However, when you type your name in the console, the name will be stored in the variable location of name. If the statement is stored in a variable name, double quotation marks are not required.

Print ("Hi. I am Felix. Do youremember me?") Name = input ("Sorry. What is your Name?") Print ("Hey!", name, ", How are You?")

Enter:

Hi. I am Felix. Do you rememberme? Sorry. What is your Name? Felix Hey! Felix,How are You?

Now when you type your name on the second line, your name will be stored in the variable name 'name'. So it can be passed through the print statement.

In python, you need to follow a set of rules when creating variable names:

Variable names can have letters (A-z), numbers (0-9), and underscores (_).

Variable names should not start with any number.

Variable names cannot have special characters.

In Python, the variable name cannot be a keyword.

VI. Introduction of data types in Python

Let me ask you three questions: what's your name? How old are you? Are you interested in learning Python? Each answer is different. The first is text-based data types, the second is digital data, and the third is classified data.

The basic classification of data types is text, numbers, and yes or no types. The reason for classifying data is that each type behaves differently. I can calculate your age in two years from your age, but I can't do the same with text-based data.

In programming, text-based data is called a string. Numerical data can be divided into two categories: one is int, the other is float. Int is an integer, while the float type is used for numbers after the decimal point. The third type, called the boolean data type, contains only two values, "True" and "False".

We have learned how to get a string from the user and how to print it to the console. It's the same with getting a numeric value, but the input value always appears as a string.

Let's continue with the scene of the park. After a while, the old friend in the park asked your age. Age is numeric data, and to ask for numeric data, the input command should be passed through int (). At this time, nature will come out again. If someone asks your age, you will say 25 or 30.

The answer is the same as the answer to other questions. But after hearing this answer, your brain will recognize it as a digital data. This is how our brains work, and int () does the same thing in programming.

Age = int (input (what is yourage?)) Print ("Your age is", age)

Output.

What is your age? 26 Your age is 26

With the help of float (), try the same operation for the float value.

1. Type () keyword

Type () is used to find the data type of the variable, such as the following code:

Name = "Felix" age = 23 print (type (name)) print (type (age))

Output

'str' 'int'

two。 Practice with comments

Comments are statements that are not considered computer instructions. These comments can be used to write developer information, code usage, or anything independent of the actual code.

There are two types of comments: single-line comments and multiline comments. Use # to create single-line comments; use''Your Command Here''to create multiline comments.

# Single Line command''' This is a multi line command'''

Operators and their functions

In programming, just storing and retrieving data is not enough. Let's look at an example. You have to go to the store to buy some chocolates. Now the price of a piece of chocolate is $4.99. You need a total of 10 chocolates. After receiving the chocolates, you have to pay the bill. Now, how do you calculate the amount?

In this case, we can store the price of chocolate in a float variable. But we have to multiply the cost by the total number of chocolates to get the total price. This is a simple elementary mathematics.

But how do computers do this? This requires the intervention of the operator. There are many operations such as multiplication in mathematics. In order to perform calculations in programming, we use symbols called operators, which usually operate on two different operands.

PRICE = 4.99COUNT = 10 TOTAL = PRICE * COUNT

The operator is *. Operators in python mainly include arithmetic operator, assignment operator, comparison operator, logical operator and bit operator.

1. Arithmetic operator

Arithmetic operators are used in basic mathematical operations, such as addition, subtraction, multiplication and division. Let's say axiom 30, bust 4.

Use the Python program of the above calculation.

A = 30 b = 4 print (a + b) print (a-b) print (a * b) print (a / b) floor = a / / b print (floor) mod = a% b power = a * * b print (mod) print (power)

Output:

34 26 120 7.5 7 2 810000

two。 Assignment operator

The assignment operator is used to assign values to variables. The main assignment operator is =.

In price = 50, assign a value of 50 to the price variable.

A = 50 b = 40 a = 60 print (a) print (b)

Output:

60 40

The variable will always get the final assignment. In the above program, the last assignment of the variable "a" is 60.

In addition to the operator =, there are also some assignment operators, that is, abbreviated operators. These operators are used to store the value returned by an operation on a particular variable into the variable itself.

+ = is a short operator. If we were to use it in programming, the syntax would be as follows. The current syntax for this expression is a = a + b. After assigning values to'a 'and' b', the result is stored in'a 'itself.

A = 40 b = 60 a + = b print (a)

Output:

one hundred

You can use other short operators (such as-=, * =, / =, * * = / / =,% =) to execute this type of program. Almost all arithmetic operators support short operations.

3. Comparison operator

The comparison operator is used to compare two variables. All comparison operators return "True" or "False". Syntax: Operand1 operator Operand2

(1) = = is the equality operator. Returns True if the two values are equal, False otherwise.

A = 10 b = 10 c = 20 print (astragalb) print (astatc)

Output:

True False

(2)! = inequality operator. It works the opposite of the equation operator and returns True only if the two values are different.

A = 10 b = 10 c = 20 print (astragalb) print (astatc)

Output:

False True

(3) > is greater than the operator. Returns True if operand1 is greater than operand2, otherwise 0.

A = 10 b = 10 c = 20 print (a > b) print (c > a) print (a > c)

Output:

False True False

(4)

< 为小于运算符。如果operand1小于operand2，则返回True，否则返回0。 a = 10 b = 10 c = 20 print(a < b) print(c < a) print(a < c) 输出： False False True (5) >

The operation of = and and =. If the value 1 is greater than or equal to the second value, the first returns True.

A = 10 b = 10 c = 20 print (a > = b) print (c > = a) print (a > = c)

Output:

True True False

Again such as

A = 10 b = 10 c = 20 print (a bor cb: print ("if conditionsatisfied") print ("Hello")

Output:

If condition satisfied Hello

(2) if. Else

In the previous example, nothing is done if the expression becomes if False:. The else keyword makes it possible. If the condition in If is False, the statement in the else section will be executed.

A = 10 b = 5 if a > b: print ("If is executed") else:

(3) if Elif... Else

If you have more than one condition in your program, use this kind of nesting condition.

A = 10 b = 5 if a > b: print ("If is executed") else:

After using the: in if, elif, and else expressions, the statement must be given after four spaces on the next line. It's called indentation.

IX. Circular statement

Looping or repeating the same type of operation is very important in programming. This method is called a loop operation.

There are two keyword types in python. One is while, the other is for.

(2) while:

Syntax: while expression

Statements in the while block are executed until each time the expression returns True.

A = 5 while a > 0: print (a) aa = Amuri 1 print ("while loop executed")

Output:

5 4 3 2 1 while loop executed

The value returned from the expression changes all the time, and at some point a becomes 0. Suppose that a > o is wrong now, and execution will stop when the while loop becomes False.

(2) for cycle

Statement: for variable in sequence

There are many sequence types available in python. But now let's create a sequence with the range () keyword.

For x in range (5): in this expression, range (5) creates a sequence from 0 to 4. Assign consecutive numbers to the variable x each time.

A = 5 for x in range (a): print (a) print ("for loop executed")

Output:

0 1 2 3 4 for loop executed

Functional programming

We have taken a look at functions such as print () and input () in Python. These functions are built into Python. In this section, we will see how to create your own functions. Functions are helpful in many cases.

Similarly, let's take the real world as an example. If you need a cake to celebrate your friend's birthday, there is only one day left. You need a cake, but you don't need to learn how to make a cake because there is a cake maker. So when we want something, we find someone who can do it for us.

Functions work in the same way, and if you create a function, it will be called multiple times anywhere in the program. For example, if another person needs cake, he can also call the same baker. In this way, the function simplifies the readability of the code and is easy to debug.

In Python, functions can be created in four different ways. As follows:

No parameters and return values

With parameters and no return value

With parameters and return values

Without parameters and return values

Let me tell you a short story to let you know about these four functions. John is a young man living in the city. His friend called him and invited him to the theatre. Because he had extra tickets, he went to the theatre. When he came back from the theatre, he saw a weighing machine. He went to the machine to check his weight. Then he went to a restaurant, ordered food, and finally went home. When he got home, he noticed an email in his mailbox.

Of course, I know this is not an interesting story. But think of everything in this story as a parameter or a return value, and it will be useful in the future.

11. How to create a function?

In python, you can use the def keyword to create a function: def function_name: to create a function.

Def add (): astat5 baked 7 print (aqb)

The above snippet is a function definition. This can be called anywhere in the program.

Remember, the function that does not return the value will be represented as the function name (); the function with the return value will be represented as the variable = the function name (); the return value will be stored in the variable.

Type 1: no parameters and return values

The theater in the story is an example of this function. In this case, any comments are made by him, he just sees an image, that does not depend on his existence, so there are no parameters and no return value.

Def hello (): print ("Hello") hello ()

The hello () function passes nothing and returns nothing.

Output:

Hello

Type 2: parameter, no return value

In the weighing machine, he saw his weight. Only when he stands on the machine will the machine show his weight. This is passing a parameter.

Def add (CJR d): print (CJD) add (4Pol 5)

Output:

nine

Type 3: parameter with return value

Take the restaurant as an example, in this case, he takes information about his money and what he needs to eat as a parameter. In return, he got food.

Def add (cMagna d): return Centrd ans = add (4 Magi 5) print (ans)

Output

nine

Type 4: parameter with no return value

Finally, the message in the mailbox is an example of having no parameters but a return value.

Def add (): axiom 6 baud 4 return ahumb ans=add () print (ans) "how to use Python language" ends here, thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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