if语句,while循环,for循环

if语句：

分支结构，选择结构

# Author:Huan
import getpass　　#引入密文密码

_username = 'Huan'
_password = 'abc'
username = input("name:")
#password = getpass.getpass("password:")
password = input("password:")

if _username == username and _password == password:
    print("Welcome user {name} login...".format(name=username))
else:
    print("Invaild username or password")

print(username,password)

while循环：

基于某种条件循环到结束。

# Author:Huan

age_of_huan = 26
count = 0
while count < 3:
    guess_age = int(input("guess age:"))
    if guess_age == age_of_huan:
        print("yes,yo1u got it.")
        break
    elif guess_age > age_of_huan:
        print("think smaller...")
    else:
        print("think bigger...")
    count += 1
else:
    print("you have tried too many times...")

for循环：

例1：

for i in range(0,10):
    if i < 5:
        print("loop",i)
    else:
        continue    #跳出本次循环，进入下次循环
    print("hello...")

例2：

# Author:Huan

age_of_huan = 26
for i in range(3):
    guess_age = int(input("guess age:"))
    if guess_age == age_of_huan:
        print("yes,you got it.")
        break
    elif guess_age > age_of_huan:
        print("think smaller...")
    else:
        print("think bigger...")
else:
    print("you have tried too many times...")

continue：跳过循环的这一次循环，进行循环的下一次操作

break：停止整个循环