python练习（一）

1.计算1-2+3-4+...+99

2.计算1-2+3-4+...+87-89+90-...-99

3.计算1-2+3-4+...+87+89-90+...+99

4.逻辑运算

print(1 and 2)      print(0 and 1)      print(1 and 0)       print(1 and 1+2)

print(0 and 1+2)  print(1>2 and 1)  print(1 and 1>2)   print(1<2 and 1)    print(1 and 1<2)

print(1 or 2)         print(1 or 0)         print(0 or 1)          print(1 or 1+2)

print(0 or 1+2)     print(1>2 or 1      print(1 or 1>2)     print(1<2 or 1)       print(1 or 1<2) 

5.用户登录，每次登录显示剩余次数，一共有三次机会

#计算1-2+3-4+...+99
sum = 0
count = 1
while count < 100:
    if count % 2 == 1:
        sum += count
    elif count % 2 == 0:
        sum -= count
    count += 1
print(sum)

#计算1-2+3-4+...+87-89+90-...-99
sum = 0
count = 1
while count < 100:
    if count % 2 == 1:
        sum += count
    elif count % 2 == 0 and count != 88:
        sum -= count
    count += 1
print(sum)

#计算1-2+3-4+...+87+89-90+...+99
sum = 0
count = 1
j = -1
while count < 100:
    if count != 88:
        j = -j
        sum += j*count
    count += 1
print(sum)
'''
50
138
-50
'''

#先and 再or
print(1 and 2) #2
print(0 and 1) #0
print(1 and 0) #0
print(1 and 1+2) #3
print(0 and 1+2) #0
print(1>2 and 1) #False
print(1 and 1>2) #False
print(1<2 and 1) #1
print(1 and 1<2) #True

print(1 or 2) #1
print(1 or 0) #1
print(0 or 1) #1
print(1 or 1+2) #1
print(0 or 1+2) #3
print(1>2 or 1) #1
print(1 or 1>2) #1
print(1<2 or 1) #True
print(1 or 1<2) #1

#5
name = '王大锤'
password = 123
i = 0
while i < 3:
    input_name = input('请输入用户名：')
    input_password = input('请输入密码：')
    i += 1
    if input_name == name and int(input_password) == password:
        print('登陆成功！')
        ret = '''
        name = %s
        password = %s
        ''' %(name,password)
        print(ret)
        break
    else:
        if i == 3:
            print('您的机会已用完！')
        else:
            print('登录失败！还剩%s次机会' %(3-i))