第1章 Python简介break是python中的一个关键字，用于将程序控件带出循环。break语句逐个打破循环，即，在嵌套循环的情况下，它首先打破内部循环然后继续到外部循环。
换句话说，我们可以说break用于中止当前程序的执行，控件转到循环后的下一行。
中断通常用于我们需要打破给定条件的循环的情况。
中断的语法如下。
#loop statements break;
例1
list =[1,2,3,4]
count = 1;
for i in list:
if i == 4:
print("item matched")
count = count + 1;
break
print("found at",count,"location");
输出：
item matched found at 2 location
例2
str = "python" for i in str: if i == 'o': break print(i);
输出：
p y t h
示例3：使用while循环的break语句
i = 0;
while 1:
print(i," ",end=""),
i=i+1;
if i == 10:
break;
print("came out of while loop");
输出：
0 1 2 3 4 5 6 7 8 9 came out of while loop
例3
n=2
while 1:
i=1;
while i<=10:
print("%d X %d = %d\n"%(n,i,n*i));
i = i+1;
choice = int(input("Do you want to continue printing the table, press 0 for no?"))
if choice == 0:
break;
n=n+1
输出：
2 X 1 = 2 2 X 2 = 4 2 X 3 = 6 2 X 4 = 8 2 X 5 = 10 2 X 6 = 12 2 X 7 = 14 2 X 8 = 16 2 X 9 = 18 2 X 10 = 20 Do you want to continue printing the table, press 0 for no?1 3 X 1 = 3 3 X 2 = 6 3 X 3 = 9 3 X 4 = 12 3 X 5 = 15 3 X 6 = 18 3 X 7 = 21 3 X 8 = 24 3 X 9 = 27 3 X 10 = 30 Do you want to continue printing the table, press 0 for no?0