What are the indentation rules of python

Python’s indentation rules: For class definitions, function definitions, flow control statements, exception handling statements, etc., the colon at the end of the line and the indentation of the next line indicate the beginning of the next code block, and the indentation The end of indicates the end of this code block. Usually, a length of 4 spaces is used as an indentation amount (a Tab key represents 4 spaces).

The operating environment of this tutorial: windows7 system, python3.7 version, DELL G3 computer

Python indentation rules

Unlike other programming languages ​​(such as Java and C language) that use braces "{}" to separate code blocks, Python uses code indentation and colons ( : ) to distinguish code blocks. between levels.

In Python, for class definitions, function definitions, flow control statements, exception handling statements, etc., the colon at the end of the line and the indentation of the next line indicate the beginning of the next code block, and the end of the indentation It indicates the end of this code block.

Note that to indent code in Python, you can use spaces or the Tab key. But whether you type a space manually or use the Tab key, a length of 4 spaces is usually used as an indentation amount (by default, a Tab key represents 4 spaces).

For example, in the following Python code (it involves knowledge that has not been learned yet, beginners do not need to understand the meaning of the code, they only need to understand the indentation rules of the code block):

height=float(input("输入身高：")) #输入身高
weight=float(input("输入体重：")) #输入体重
bmi=weight/(height*height)       #计算BMI指数
#判断身材是否合理
if bmi<18.5:
    #下面 2 行同属于 if 分支语句中包含的代码，因此属于同一作用域
    print("BMI指数为："+str(bmi)) #输出BMI指数
    print("体重过轻")
if bmi>=18.5 and bmi<24.9:
    print("BMI指数为："+str(bmi)) #输出BMI指数
    print("正常范围，注意保持")
if bmi>=24.9 and bmi<29.9:
    print("BMI指数为："+str(bmi)) #输出BMI指数
    print("体重过重")
if bmi>=29.9:
    print(BMI指数为："+str(bmi)) #输出BMI指数
    print("肥胖")

Python has very strict requirements for code indentation. The indentation amount of code blocks at the same level must be the same, otherwise the interpreter will report a SyntaxError exception. For example, if you make incorrect changes to the above code, set the indentation of 2 lines of code in the same scope to 4 spaces and 3 spaces respectively, as follows:

if bmi<18.5:
    print("BMI指数为："+str(bmi)) #输出BMI指数
   print("体重过轻")

Beginners can understand the Python indentation rules this way. Python requires that each line of code belonging to the same scope must have the same indentation amount, but there is no hard and fast rule about the specific indentation amount. .

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