#for 循环的嵌套结构:
# for 变量1 in 可迭代对象:
# for 变量2 in 可迭代对象:
# 语句1
# 语句2
# 语句3
# 语句4
案例1:
打印
*****
****
***
**
*
for i in range(0,5):
for j in range(0,5-i):
print('*',end='')
print()
案例2:打印乘法口诀表
for i in range(1,10): #行数
for j in range(1,i+1): #列数
print('%i*%i=%i' %(j, i, i*j), end='\t')
print()
案例3:1234四个数,求无重复且互不相同的组合
for i in (1,2,3,4):
for j in (1,2,3,4):
for k in (1,2,3,4):
if (i!=j) and (i!=k) and (j!=k):
print(i,j,k)
案例4:登录
error_num=0
yonghu= True
while yonghu:
print('===登录系统===')
user = input('请输入用户名:')
password = input('请输入密码:')
if user =='guanxiu' and password =='123456':
print('登录成功')
yonghu =False
elif user=='' or password=='':
print('用户名或密码不能为空!')
elif user=='' and password=='':
print('请输入用户名!')
else:
error_num+=1
if (error_num==3):
print('用户名或密码错误超过3次,账号冻结!')
yonghu=False
else:
print('用户名密码不匹配,请重新输入!')
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