python基础之字典

字典是一系列键值对，每个键都与一个值相关联。

访问字典的值

alien = {'color':'green','points':5}
new_points = alien['points']   
print("You just earned " + str(new_points) + " points!")

#get访问到没有的key也不会报错
alien = {'color':'green','points':5}
new_points = alien.get('points')
new_none = alien.get('name')   
new_name = alien.get('name','huny')
print(new_points)
print(new_none)
print(new_name)

添加键值对

alien = {'color':'green','points':5}
alien['x_position'] = 0
alien['y_position'] = 25
print(alien)

修改字典的值

alien = {'color':'green','points':5}
alien['color'] = 'yellow'
print(alien)

删除键值对

alien = {'color':'green','points':5}
print(alien)
del alien['points']
print(alien)

遍历字典

user = {'username':'efermi','first':'enrico','last':'fermi'}
for key,value in user.items():
	print("\nkey:" + key)
	print('value:' + value)

遍历字典的键

user = {'username':'efermi','first':'enrico','last':'fermi'}
for key in user.keys():
	print("\nkey:" + key)

遍历字典的值

user = {'username':'efermi','first':'enrico','last':'fermi'}
for value in user.values():
	print("\nvalue:" + value)

字典嵌套列表

favorite_languages = {
'jen':['python','ruby'],
'sarah':['c'],
'edward':['ruby','go'],
}
for name,languages in favorite_languages.items():
	print("\n" + name.title() + "is favorite_languages are:")
	for language in languages:
		print("\t" + language.title())

字典嵌套字典

users = {
	'aeinstein':{
		'first':'albert',
		'last':'einstein',
		'location':'princeton',
	},

	'mcurie':{
		'first':'marie',
		'last':'curie',
		'location':'paris',
	}
}

for username,user_info in users.items():
	print("\nusername： " + username)
	full_name = user_info['first'] + " " + user_info['last']
	location = user_info['location']

	print("\tfull_name: " + full_name.title())
	print("\tlocation: " + location.title())