python基础知识回顾[1]

1.声明变量

# 声明一个变量name用来存储一个字符串'apollo'
name = 'apollo'
# 声明一个变量age用来存储一个数字20
age = 20

# 在控制台打印变量name中存储的字符串和变量age中存储的数字
# 打印结果:apollo 20
print(name,age)

# 在控制台打印字符串"name"和"age"
print('name','age')
# 打印结果:name age

2.控制台交互

username = input('please input your username :')
password = input('please input your password :')
print('当前登录用户:', username, password)

please input your username :apollo
please input your password :111111
当前登录用户: apollo 111111

3.逻辑运算

# == , != , <= , >= , < , >  逻辑运算符
print(1 == 1)               # True
print(1 == 2)               # False
print(1 == "")             # False
print(1 != 2)               # True
print(1 != 1)               # False
print(1 <= 2)               # True
print(1 >= 2)               # False
print(1 < 2)                # True
print(1 > 2)                # False

print(1 == 1 and 2 == 2)      # True
print(1 == 1 and 1 == 2)      # False
print(2 == 1 and 1 == 2)      # False

print(1 == 1 or 2 == 2)      # True
print(1 == 1 or 1 == 2)      # True
print(2 == 1 or 1 == 2)      # False

print(not 1 == 1)              # False
print(not 1 == 2)              # True

4.流程控制

##1 如果if跟随的条件为真,那么执行属于if中的语句
if 1 == 1:
    print("1==1真的")

##2 如果if跟随的条件为假,那么不执行属于if的语句,然后寻找else,执行属于else中的语句
if 1 == 2:
    print("假的")
else:
    print("1==2假的")

##3 如果if条件不成立,会进行第二次判断elif,如果elif条件成立,则执行属于elif中的语句,如不成立则else
if 1 == 2:
    print("1==2")
elif 1 == 1:
    print("1==1")
else:
    print("全是骗人的")    

##4 for循环
for i in range(10):
    # 当i为5时,停止当次循环回到最开始继续循环
    if i == 5:
        continue
    # 当i为7时,停止全部循环
    if i == 7:
        break
    # 打印结果: 0,1,2,3,4,6
    print(i)

##5 死循环
a = 0
sum = 0
while a < 10:
    a += 1
    sum += a
print(sum)

while True:
    username = input("username:")
    password = input("password:")
    if username == "apollo" and password == "":
        print("successful")
        break
    else:
        continue