Python基础之dictionary

简介

字典是一种可变容器模型，且可存储任意类型对象，字典的每个键值 key=>value对用冒号:分割，每个键值对之间用逗号 , 分割，整个字典包括在花括号{} 中 ，如：

object = {
	'color': 'yellow', 
	'size': 'big'
}
print(object['color'])
print(object['size'])

添加键值对

object['age'] = 18
object['sex'] = 'man'
print(object)

创建一个空字典

object = {}
object['color'] = 'yellow'
object['size'] = 'big'
print(object)

修改字典中的值

object['color'] = 'black'
print(object)

删除键值对

object = {'color': 'black', 'age': 18}
del object['color']
print(object)

遍历键值对

user = {
	'username': 'coisini',
	'age': '18',
	'sex': 'man'
}
for key,value in user.items():
	print('key:' + key)
	print('value:' + value)

遍历所有键值

use_languages = {
	'one_user': 'python',
	'two_user': 'c',
	'three_user': 'ruby',
	'four_user': 'python'
}
for key in use_languages.keys():
	print('key:' + key)
	print('value:' + use_languages[key])
	
	if key == 'one_user':
		print('one_user is in use_languages')

use_languages.key() 简写为use_languages

if 'four_user' in use_languages:
	print('four_user is in use_languages')

顺序遍历所有键值

for name in sorted(use_languages.keys()):
	print(name.title())

遍历字典中的所有值

for language in use_languages.values():
	print(language.title())

使用集合（set）剔除重复项

for language in set(use_languages.values()):
	print(language.title())

列表字典嵌套

one_user = {'color': 'black', 'age': 5}
two_user = {'color': 'white', 'age': 10}
three_user = {'color': 'yellow', 'age': 15}

users = [one_user, two_user, three_user]
for user in users:
	print(user)

字典列表嵌套

user = {
	'username': 'coisini',
	'languages': ['Java', 'Python']
}
	
for language in user['languages']:
	print('	' + language)

字典字典嵌套

users = {
	'coisini': {
		'name': 'coisini',
		'age': 18,
		'location': 'China'
	},
	'maggieq': {
		'name': 'maggieq',
		'age': '22',
		'location': 'Canada'
	}
}

for username, userinfo in users.items():
	print('
username:' + username)
	
	for key, val in users[username].items():
		print('	key:' + str(key))
		print('	val:' + str(val))

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