PYTHON之路
七、基本的if判断
最简单的流程处理： if ...else
If简单练习：
#!/usr/bin/env python
# -*-coding:utf-8 -*-
#if 基本表达式
#用户登录验证
#提示输入用户名和密码
#验证用户名和密码
#如果错误，则输出用户名或密码错误；
#如果成功，则输出欢迎,XXX！
user = 'zhang'
password = '123.com'
username = input("username:")
password = input("password:")
if user == username:
print("用户名输入正确") {下层代码}
下层代码：
这个代码的运行要依赖于上一层代码，也就是说上一层代码必须为真（成立），才会读下层代码。///可以理解为上一层的子代码
子代码不能顶行写，否则Python认为是不相关的代码，将会独立执行
Python的默认开发规范：子代码空4格
If ...else语句练习：
#!/usr/bin/env python
# -*-coding:utf-8 -*-
user = 'zhangjianghua'
passwd = '123.com'
username = input("username:")
password = input("password:")
if user == username :
print("username is correct...")
if password == passwd:
print("welcome login...")
else:
print("password is invalid...")
else:
print("连用户名都没蒙对，滚粗。。。")
If...else V2 优化版：
#!/usr/bin/env python
#-*-coding:utf-8 -*-
user = "zhangjianghua"
passwd = "123.com"
username = input("username:")
password = input("password:")
if user == username and passwd == password:
print("welcome login")
else:
print("Invalid username or password....")
八、猜年龄游戏
（猜年龄游戏V1，猜对即退出）
#!/usr/bin/env python
#-*-coding:utf-8 -*-
age = 19
guess_num = int (input("input your guess num:"))
if guess_num ==age:
print("Congratulations! you got it.")
elif guess_num >age:
print("Think smaller!")
else:
print("Think Big...")
九、for循环
for i in range(10):
print(i)
i 每循环一次i 就会增加1
(猜年龄游戏V2，最大次数三次)
#!/usr/bin/env python
#-*-coding:utf-8 -*-
age = 19
for i in range(10):
if i <3:
guess_num = int(input("input your guess num:"))
if guess_num ==age :
print("恭喜你猜对了")
break #猜对即停止，不往后走了，跳出整个loop
elif guess_num >age:
print("往小了想！")
else:
print("往大了想！")
else:
print("尝试了太多次..拜拜~~")
break
（猜年龄游戏V3，最大循环10次，每3次重新循环）
#!/usr/bin/env python
#-*-coding:utf-8 -*-
#Author: ZhangJiangHua
age = 19
counter =0
for i in range(10):
print('--counter:',counter)
if counter <3:
guess_num = int(input("input your guess num:"))
if guess_num == age :
print("恭喜你，猜对了！")
break #不往后走了，跳出整个循环
elif guess_num >age:
print("往小了猜！")
else:
print("往大了猜！")
else:
continue_confirm = input("还要继续吗？y|n")
if continue_confirm == 'y':
counter = 0
continue #(跳出当次循环，而不是整个)
else:
print("bye")
break
counter +=1 #counter = counter +1