python基础for循环和while循环（十）

while：循环 

a = 10

while a > 0:
    print(a)

print('结束')

for循环：

a = '12345'
for item in a:
    print(item)
b = [1, 2, 3, 4]
for item in b:
    print(item)
c = ('a', 'b', 'c', 'd')
for item in c:
    print(item)
d = {
    1: 'a',
    2: 'b',
    3: 'c'
}
# 打印出字典的key和value
for a,b in d.items():
    print("{}-{}".format(a,b))
e = {1, 2, 3, 5, 9}

# for a, b in d.items():
#     print('{}={}'.format(a, b))

# for item in e:
#     print(item)
# 打印1到20的数字
for item in range(1, 20):
    print(item)
# 表示从1到20每间隔4个数打印一次
for item in range(1, 20,4):
    print(item)

循环的关键字：

# break
# 表示0-9都可以打印出来，左关右开
for i in range(10):
    print(i)
    if i % 2 != 0:
        break


# continue
for i in range(10):
    if i % 2 == 0:
        continue
    print(i)