《Python 编程-从入门到实践》5-1~5-13

5-1 条件测试：编写一系列条件测试；将每个测试以及你对其结果的预测和实际结果都打印出来。

name = 'Li Mei'
print("Is name=='Li Mei'?I predict True.")
print(name=='Li Mei')

print("Is name=='Li Lei'?I predict False.")
print(name=='Li Lei')

5-6 人生的不同阶段：设置变量age的值，再编写一个if-elif-else结构，根据age的值判断处于人生的哪个阶段。

age = 3
if age < 2:
	print("He's a baby.")
elif 2<=age and age<4:
	print("He is a toddler")
elif 4<=age and age<13:
	print("He is a child")
elif 13<=age and age<20:
	print("He is a teenager")
elif 20<=age and age<65:
	print("He is an adult")
elif 65<=age:
	print("He is an old man")

5-8 以特殊方式跟管理员打招呼：创建一个至少包含5个用户名的列表，且其中一个用户名为‘admin’。想象你要编写代码，在每位用户登录网站后都打印一条消息，遍历用户名列表，并向每位用户打印一条问候消息。

usernames = ['admin','Eric','Li Lei']
for username in usernames:
	if username == 'admin':
		print("Hello admin,would you like to see a status report?")
	else:
		print("Hello "+username+", thank you for logging in again.")

5-9 处理没有用户的情况。在为完成练习5-8编写的程序中，添加一条if语句，检查用户名列表是否为空。

usernames = []
if len(usernames)==0:
	print("We need to find some users!")
else:
	for username in usernames:
		if username == 'admin':
			print("Hello admin,would you like to see a status report?")
		else:
			print("Hello "+username+", thank you for logging in again.")