模拟现实世界中的情形
大多数程序都旨在解决最终用户的问题
第5章 if语句
条件测试
特定值是否包含在列表中 in
5.3 if-elif-else结构
如果你只想执行一个代码块，就使用if-elif-else结构，如果要运行多个代码块，就使用一系列独立的if语句。
动手试一试：
#5-3 外星人颜色#1
alien_color='green'
if alien_color=='green':
print('This player got 5 points!')
alien_color='red'
if alien_color=='green':
print('This player got 5 points!')
#2
alien_color='green'
if alien_color=='green':
print('This player got 5 points!')
else:
print('This player got 10 points!')
alien_color='yellow'
if alien_color=='green':
print('This player got 5 points!')
else:
print('This player got 10 points!')
#3
alien_color='green'
if alien_color=='green':
print('This player got 5 points!')
elif alien_color=='yellow':
print('This player got 10 points!')
else:
print('This player got 15 points!')
alien_color='yellow'
if alien_color=='green':
print('This player got 5 points!')
elif alien_color=='yellow':
print('This player got 10 points!')
else:
print('This player got 15 points!')
alien_color='green'
if alien_color=='red':
print('This player got 5 points!')
elif alien_color=='yellow':
print('This player got 10 points!')
else:
print('This player got 15 points!')
age=32
if age<2:
print('He is a baby!')
elif age>=2 and age<4:
print('He is toddling!')
elif age>=4 and age<13:
print('He is a child!')
elif age>=13 and age<20:
print('He is a teenager!')
elif age>=20 and age<65:
print('He is an adult!')
else:
print('He is an aged man!')
favorite_fruits=['orange','cherry','watermelon']
if 'orange' in favorite_fruits:
print("You really like orange!")
if 'cherry' in favorite_fruits:
print("You really like cherry!")
if 'apple' in favorite_fruits:
print("You really like apple!")
if 'pear' in favorite_fruits:
print("You really like pear!")
if 'watermelon' in favorite_fruits:
print("You really like watermelon!")
5.4 使用if语句处理列表
确定列表不是空的 if requested_toppings:
动手试一试：
#5-8 以特殊方式跟管理员打招呼
users=['admin','bing','yang','ling','fei']
for user in users:
if user=='admin':
print('Hello admin,would you like to see a status report?')
else:
print('Hello '+user.title()+",thank you for logging in again!")
users=[]
if users:
for user in users:
if user=='admin':
print('Hello admin,would you like to see a status report?')
else:
print('Hello '+user.title()+",thank you for logging in again!")
else:
print('We need to find some users!')
current_users=['admin','bing','yang','ling','fei']
new_users=['wang','Bing','Yang','wen','ma']
for new_user in new_users:
if new_user.lower() not in current_users:
print(new_user.lower()+',This user is available!')
else:
print(new_user.lower()+',This user is forbidden!')
sequences=list(range(1,10))
for sequence in sequences:
if sequence<=3 :
if sequence==1 :
print('1st')
if sequence==2 :
print('2nd')
if sequence==3 :
print('3rd')
else:
print(str(sequence)+'th')
第6章 字典
键值对
alien_0={}
alien_0['color']='green'
删除键值对
del alien_0['points']
动手试一试：
# 6-1 人
people={
'first_name':'xia',
'last_name':'wang',
'age':32,
'city':'beijing'
}
print(people['first_name'])
print(people['last_name'])
print(people['age'])
print(people['city'])
print('first_name\n\t'+people['first_name'])
1、遍历字典
for key,value in user_0.items():
for name in favorite_language.keys(): 等价于for name in favorite_language：
for language in favorite_language.values():
集合类似于列表，但每个元素都必须是独一无二的
for language in set(favorite_language.values()):
嵌套
1、在列表中存储字典
for alien_number in range(0,30):
new_alien={}
aliens.append(new_alien)
# 字典列表
aliens=[]
for alien_number in range(0,30):
new_alien={'color':'green','points':5,'speed':'slow'}
aliens.append(new_alien)
for alien in aliens[0:3]:
if alien['color']=='green':
alien['color']='yellow'
alien['speed']='medium'
alien['points']=10
elif alien['color']=='yellow':
alien['color']='red'
alien['speed']='fast'
alien['points']=15
for alien in aliens:
print(alien)
2、在字典中存储列表
# 2、在字典中存储列表
favorite_languages={
'jen':['python','ruby'],
'sarah':['c'],
'edward':['ruby','go'],
'phil':['python','haskell']
}
for name,languages in favorite_languages.items():
if len(languages)>1:
print(name.title()+"'s favorite languages are:")
else:
print(name.title()+"'s favorite language is:")
for language in languages:
print("\t"+language.title())
3、在字典中存储字典