Python 简明教程

Python - Nested if Statement

Python 支持 nested if statements ，这意味着我们可以在现有 if statement 中使用条件 if 和 if…​else statement 。

Python supports nested if statements which means we can use a conditional if and if…​else statement inside an existing if statement.

在初始条件变为真之后，可能会出现需要检查其他条件的情况。在这种情况下，可以使用嵌套 if 构造。

There may be a situation when you want to check for additional conditions after the initial one resolves to true. In such a situation, you can use the nested if construct.

此外，在嵌套 if 构造内，可以将 if…​elif…​else 构造包含在另一个 if…​elif…​else 构造内。

Additionally, within a nested if construct, you can include an if…​elif…​else construct inside another if…​elif…​else construct.

Syntax of Nested if Statement

带有 else 条件的嵌套 if 构造的语法如下：

The syntax of the nested if construct with else condition will be like this −

if boolean_expression1:
   statement(s)
   if boolean_expression2:
      statement(s)

Flowchart of Nested if Statement

以下是 Python 嵌套 if 语句的流程图：

Following is the flowchart of Python nested if statement −

nested if statement

Example of Nested if Statement

以下示例演示了嵌套 if 语句的工作方式：

The below example shows the working of nested if statements −

num = 36
print ("num = ", num)
if num % 2 == 0:
   if num % 3 == 0:
      print ("Divisible by 3 and 2")
print("....execution ends....")

运行上述代码时，将显示以下结果：

When you run the above code, it will display the following result −

num =  36
Divisible by 3 and 2
....execution ends....

Nested if Statement with else Condition

如前所述，我们可以在 if 语句中嵌套 if-else 语句。如果 if 条件为真，则执行第一个 if-else 语句，否则将执行 else 块内的语句。

As mentioned earlier, we can nest if-else statement within an if statement. If the if condition is true, the first if-else statement will be executed otherwise, statements inside the else block will be executed.

Syntax

带有 else 条件的嵌套 if 构造的语法如下：

The syntax of the nested if construct with else condition will be like this −

if expression1:
   statement(s)
   if expression2:
      statement(s)
   else
      statement(s)
else:
   if expression3:
      statement(s)
   else:
      statement(s)

Example

现在让我们来看一个 Python 代码来了解它的工作原理 −

Now let’s take a Python code to understand how it works −

num=8
print ("num = ",num)
if num%2==0:
   if num%3==0:
      print ("Divisible by 3 and 2")
   else:
      print ("divisible by 2 not divisible by 3")
else:
   if num%3==0:
      print ("divisible by 3 not divisible by 2")
   else:
      print ("not Divisible by 2 not divisible by 3")

当执行以上代码时，它会产生以下 output -

When the above code is executed, it produces the following output −

num = 8
divisible by 2 not divisible by 3
num = 15
divisible by 3 not divisible by 2
num = 12
Divisible by 3 and 2
num = 5
not Divisible by 2 not divisible by 3