python之循环
1.while
1 # while 2 #当while循环开始后，先判断条件是否满足，如果满足就执行循环体内的语句， 3 # 执行完毕后再回来判断条件是否满足，如此无限重复；直到条件不满足时，执行while循环后边的语句。 4 name = "" 5 while not name: 6 name = input("Enter your name:") 7 print("hello ,your name is ",name)
输出结果：
Enter your name: Enter your name:zyt hello ,your name is zyt
2.for循环
示例一：遍历列表
1 # for循环 2 for looper in [1,2,3,4]: 3 print(looper)
输出结果：
1 2 3 4
示例二：遍历字典
1 # 遍历字典 2 d = {"num1":1,"num2":2,"num3":3} 3 for key in d : 4 print(key,"=",d[key])
输出结果：
num1 = 1 num2 = 2 num3 = 3
示例三：range()函数
1 # range()内建函数，range（上限、下限、步长），无上限时，默认从0开始 2 for number in range(1,5): 3 print(number) 4 print("——range（）无上限时，默认从0开始——") 5 for number in range(5): 6 print(number)
输出函数：
1
2
3
4
——range（）无上限时，默认从0开始——
0
1
2
3
4
3.并行迭代，考虑两个列表元素有的长度是否一致，不一致时使用zip
1 #并行迭代 2 names = ["anne","beth","alice","bela"] 3 ages = [1,2,3,4] 4 for i in range(len(names)): 5 print(names[i]," is ",ages[i]) 6 # 并行迭代，考虑两个列表元素有的长度是否一致，不一致时使用zip 7 print("---------------zip--------------------") 8 names1 = ["anne","beth","alice","bela","bob"] 9 ages1 = [1,2,3,4] 10 for names1,ages1 in zip(names1,ages1): 11 print(names1," is ",ages1)
运行结果：
anne is 1 beth is 2 alice is 3 bela is 4 ---------------zip-------------------- anne is 1 beth is 2 alice is 3 bela is 4
4.按索引迭代
1 # 按索引迭代 2 names = ["anne","beth","alice","bela","bob"] 3 index = 0 4 for name in names: 5 if "ob" in name: 6 names[index] = "tom" 7 index +=1 8 print(names)
输出结果：
['anne', 'beth', 'alice', 'bela', 'tom']
5.continue与break
continue:跳出本次循环，进入下一次循环
break:跳出本次循环，终止循环
1 # contine 与break 2 # continue:跳出本次循环，进入下一次循环 3 # break:跳出本次循环，终止循环 4 for i in range(1,5): 5 if i==3: 6 continue 7 print(i) 8 print("---------break-----------") 9 for i in range(1,5): 10 if i==3: 11 break 12 print(i)
输出结果：
1
2
4
---------break-----------
1
2
