python基础流程控制

流程控制主要分为三大类：

1、if 判断语句

2、while 循坏语句

3、for 循坏语句

下面以举例说明：

if 判断语句：

user1 = 'seven'
user2 = 'alex'
password1 = 123
count = 0
while True:
    if count >= 3:
        print('end')
        break
    user = input('用户名：')
    password = int(input('密码：'))
    if (user == user1 or user == user2) and password == password1:
        print('登入成功')
        break
    else:
        print('登入失败')
        count += 1
        print('错误次数', count)

while 循环语句：

password = '
count = 0
tag = 1
while tag:
    if count == 3:
        print('账户锁定')
        break
    user = input('请输入用户名：')
    password1 = input('请输入密码：')
    if user == username and password1 == password:
        while tag:
            a = input('>>:')
            if a == '退出':
                tag = 0
            else:
                print(f'执行{a}命令')
    else:
        print('输入错误')
        count += 1

for 循序语句：

# 9*9乘法口诀
for i in range(1, 10):
    for j in range(1, i + 1):
            print(f'{i}*{j}={i * j}', end='\t')
    print()

结果：

1*1=1
2*1=2 2*2=4
3*1=3 3*2=6 3*3=9
4*1=4 4*2=8 4*3=12 4*4=16
5*1=5 5*2=10 5*3=15 5*4=20 5*5=25
6*1=6 6*2=12 6*3=18 6*4=24 6*5=30 6*6=36
7*1=7 7*2=14 7*3=21 7*4=28 7*5=35 7*6=42 7*7=49
8*1=8 8*2=16 8*3=24 8*4=32 8*5=40 8*6=48 8*7=56 8*8=64
9*1=9 9*2=18 9*3=27 9*4=36 9*5=45 9*6=54 9*7=63 9*8=72 9*9=81

练习题：

# 求1-100的所有数的和
sum1 = 0
for i in range(101):
    sum1 += i
print(sum1)

结果：5050

#使用 while循环输出1234568910
count = 0
l1 = range(0, 11)
len(range(0, 11))
while count < len(range(1, 11)):
    count += 1
    if count == 7:
        continue
    else:
        print(l1[count])

结果：

1
2
3
4
5
6
8
9
10

# 输出1-100的所有奇数
# for i in range(1,100,2):
#     print(i)
count = 1
while count <= 100:
    if count % 2 != 0:
        print(count)
    count += 1

结果：

1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
49
51
53
55
57
59
61
63
65
67
69
71
73
75
77
79
81
83
85
87
89
91
93
95
97
99

# 求1-2+3-4+5-.....99的所有数之和
sum1 = 0
sum2 = 0
sum3 = 0
for i1 in range(1, 100, 2):
    sum1 += i1
print(sum1)
for i2 in range(2, 100, 2):
    sum2 += i2
print(sum2)
sum3 = sum1 - sum2
print(sum3)

结果：

2500
2450
50

# 猜年龄
age = 18
tab = True
count = 1
while tab:
    age1 = input('请您猜测我的年龄：')
    age1 = int(age1)
    if age1 == age:
        print('恭喜您猜对了')
        tab = False
        break
    elif count >= 3:
        a = input('猜错啦，请问是否要继续猜测年龄呢：')
        if a == 'y' or a == 'Y':
            count = 1
            continue

#     *
#    ***
#   *****
#  *******
# *********

a = int(input('行数：'))
for i in range(1, a+1):
    print(' '*(a - i), end='')
    print('*'*(2 * i - 1))

结果：

    *
   ***
  *****
 *******
*********