杨桃的Python基础教程——第6章：Python控制结构（三）循环结构——for循环

本人CSDN博客专栏：https://blog.csdn.net/yty_7
Github地址：https://github.com/yot777/Python-Primary-Learning

6.3 循环结构——for循环

Python的for循环可以遍历任何序列的项目，如一个列表或者一个字符串。

for循环的一般格式如下：

for <variable> in <sequence>:

else:

循环语句可以加入else、break、 continue、pass关键字，作用如下：

1、else语句

如果在穷尽列表后(以for循环)或条件变为假(以while循环)循环终止时被执行

2、break语句

用来跳出for和while的整个循环体。一旦跳出，循环中任何剩下的程序块（包括else）将不执行。

3、continue语句

用来跳过当前循环块中的剩余语句，然后继续进行下一轮循环。

4、pass语句，继续当前循环，相当于没有任何作用

Python——for循环和break、else举例1

edibles = ["ham","eggs","spam","nuts"]
for food in edibles:
#edibles列表遍历到spam的时候，执行print("No more spam please!")语句，然后跳出循环
  if food == "spam":   
    print("No more spam please!")
    break
  print("Great, delicious " + food)
else:
  print("I am so glad: No spam!")
print("Finally, I finished stuffing myself.")


运行结果：
Great, delicious ham
Great, delicious eggs
#edibles列表遍历到spam的时候，执行print("No more spam please!")语句，然后跳出循环
No more spam please! 
Finally, I finished stuffing myself.

Python——for循环和break、else举例2

edibles = ["ham","eggs","nuts"]
for food in edibles:
#列表edibles没有spam
  if food == "spam":      
    print("No more spam please!")
    break
  print("Great, delicious " + food)
#列表edibles没有spam，因此执行else的print("I am so glad: No spam!")语句
else:      
  print("I am so glad: No spam!")
print("Finally, I finished stuffing myself.")

运行结果：
Great, delicious ham
Great, delicious eggs
Great, delicious nuts
#列表edibles没有spam，因此执行else的print("I am so glad: No spam!")语句
I am so glad: No spam!    
Finally, I finished stuffing myself.

Java ——for循环和break 举例

public class Test4 {
  public static void main(String[] args) {
    String[] edibles = {"ham","eggs","nuts"};
    int i=0;
    for (String food : edibles){
        if(food == "spam"){
            System.out.println("No more spam please!");
            break;
        }
        System.out.println("Great, delicious " + food);
        i=i+1;
    }  //Java的for循环没有最后的else，如果要实现Python里for-else功能需要自己写逻辑
    if(i==edibles.length){
      System.out.println("I am so glad: No spam!");
    }
    System.out.println("Finally, I finished stuffing myself.");
  }
}

运行结果：
Great, delicious ham
Great, delicious eggs
Great, delicious nuts
I am so glad: No spam!
Finally, I finished stuffing myself.

Python——for循环和continue举例

edibles = ["ham","eggs","spam","nuts"]
for food in edibles:
    #edibles列表遍历到spam的时候，跳过当前循环块的剩余语句，然后继续进行下一轮循环
    if food == "spam":                          
        continue
    print("Great, delicious " + food)
print("Finally, I finished stuffing myself.")

运行结果：
Great, delicious ham
Great, delicious eggs
#edibles列表遍历到spam的时候，跳过当前循环块的剩余语句，然后继续进行下一轮循环
Great, delicious nuts   
Finally, I finished stuffing myself.

Python——for循环和pass举例

edibles = ["ham","eggs","spam","nuts"]
for food in edibles:
    #edibles列表遍历到spam的时候，pass语句不起任何作用，仍然print("Great, delicious " + food)
    if food == "spam":   
        pass             
    print("Great, delicious " + food)
print("Finally, I finished stuffing myself.")

运行结果：
Great, delicious ham
Great, delicious eggs
#edibles列表遍历到spam的时候，pass语句不起任何作用，仍然print("Great, delicious " + food)
Great, delicious spam 
Great, delicious nuts
Finally, I finished stuffing myself.

参考教程：

廖雪峰的Python教程

https://www.liaoxuefeng.com/wiki/1016959663602400

廖雪峰的Java教程

https://www.liaoxuefeng.com/wiki/1252599548343744

Python3 教程 | 菜鸟教程
https://www.runoob.com/python3/

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杨桃的Python基础教程——第6章：Python控制结构（三）循环结构——for循环

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