Catalog

One 、 Process control classification

Two 、 Three processes of program execution

3、 ... and 、 The definition of judgment

Four 、if Judge the basic syntax of a sentence

5、 ... and 、else Judgment statement

6、 ... and 、if-else Illustrate with examples - To determine the age

7、 ... and 、 The combination of judgment statements and logical operators

8、 ... and 、 The judgment statement is illustrated with logical operators

Nine 、elif Multiple judgments

Ten 、elif Examples of multiple judgments

11、 ... and 、if Nesting of

Twelve 、if Examples of nesting

13、 ... and 、 Comprehensive quotation - Rock-paper-scissors

fourteen 、 The treatment of random numbers

15、 ... and 、Debug debugging

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One 、 Process control classification

• Judgment statement ：if
• Loop statement ：while loop and for loop

Two 、 Three processes of program execution

3、 ... and 、 The definition of judgment

• If the conditions are met , To do something .
• If the conditions are not met , Just do something else , Or do nothing .
• Be careful ： The keywords involved in the judgment statement are if、else、elif.

Four 、if Judge the basic syntax of a sentence

• You can put the whole if Statement as a complete block of code .
• The code is indented with a tab key , Or four spaces .
• stay Python In development ,tab Keys and spaces cannot be mixed .
• pycharm Can be used directly in tab Key to complete code indentation , Because the default setting will automatically set a tab Key to four spaces .

5、 ... and 、else Judgment statement

• Used to deal with situations where conditions are not met .

• if and else Statements and their indented parts together are a complete block of code .
• else Keywords must be the same as if A combination of , Not to be used alone .

6、 ... and 、if-else Illustrate with examples - To determine the age

• Define an integer variable to record age .
• Judge whether it is full 18 year （>=）.
• If full 18 One year old , Allow to enter the Internet bar hi pi .

7、 ... and 、 The combination of judgment statements and logical operators

• In program development , Usually when judging conditions , Will need Judge multiple conditions at the same time .
• Only Multiple conditions are met , only Can execute new follow-up code , At this time, we need to make be used Logical operators .

8、 ... and 、 The judgment statement is illustrated with logical operators

• Define an integer variable age, Write code to determine whether the age is correct .
• The required person's age is 0~120 Between the ages of .

• Define two integer variables python_score、c_score Write code to judge performance .
• It is required that only one score is greater than 60 Points are qualified .

• Define a boolean variable is_employee, Write code to judge whether it is an employee of the company .
• If not , Prompt: no entry allowed .

Nine 、elif Multiple judgments

• Application scenarios ： When judging conditions , Multiple criteria are required , And the code to be executed corresponding to the unused conditions .
• Be careful ：elif and else And if A combination of , It can't be used alone .

Ten 、elif Examples of multiple judgments

11、 ... and 、if Nesting of

• Application scenarios ： When the previous conditions are met , Add additional judgment .
• Be careful ： Partially through if Nested variables for judgment , Need to be defined as a local variable .

Twelve 、if Examples of nesting

• Define Boolean variables has_ticket Indicates whether there is a ticket .
• Define integer variables knife_length Indicates the length of the knife , Company cm.
• First, check whether there is a ticket , If there is , To allow security checks .
• At security check , The length of the knife needs to be checked , Judge whether it exceeds 20cm.

• If you don't have a ticket, you are not allowed to enter the door .

13、 ... and 、 Comprehensive quotation - Rock-paper-scissors

• Enter the punch you want from the console ,1： stone 、2： scissors 、3： cloth .
• The computer punches at random - Let's assume that computers can only make stones , Complete the overall code function .
• Compare the outcome .

fourteen 、 The treatment of random numbers

• First step ： stay python in , To use random numbers , First, you need to import the module of random numbers （ tool kit ）.

• The second step ： call random Module randint Method can generate random numbers .

15、 ... and 、Debug debugging

• effect ： View code execution
• Operation steps ：

• Be careful ：

• Right click , Choose “Debug' file name '” Run code .
• Step by step , View the execution process .