python之循环

1.while

# while
#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，
# 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。
name = ""
while not name:
    name = input("Enter your name:")
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

# for循环
for looper in [1,2,3,4]:
    print(looper)

　　输出结果：

1
2
3
4

　　示例二：遍历字典

# 遍历字典
d = {"num1":1,"num2":2,"num3":3}
for key in d :
    print(key,"=",d[key])

　　输出结果：

num1 = 1
num2 = 2
num3 = 3

　　示例三：range()函数

# range()内建函数，range（上限、下限、步长），无上限时，默认从0开始
for number in range(1,5):
    print(number)
print("——range（）无上限时，默认从0开始——")
for number in range(5):
    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

#并行迭代
names = ["anne","beth","alice","bela"]
ages = [1,2,3,4]
for i in range(len(names)):
    print(names[i]," is ",ages[i])
# 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
print("---------------zip--------------------")
names1 = ["anne","beth","alice","bela","bob"]
ages1 = [1,2,3,4]
for names1,ages1 in zip(names1,ages1):
    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

# 按索引迭代
names = ["anne","beth","alice","bela","bob"]
index = 0
for name in names:
    if "ob" in name:
        names[index] = "tom"
    index +=1
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

# contine 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
for i in range(1,5):
    if i==3:
        continue
    print(i)
print("---------break-----------")
for i in range(1,5):
    if i==3:
        break
    print(i)

　　输出结果：

1
2
4
---------break-----------
1
2