Python 字典
Python 字典：是一系列的键与值得对，与键相关联的值可以是数字，字符串，列表乃至字典。
Python中字典用放在花括号{} 中的一系列的键与值对表示
如：alien_0 = {'color': 'green'}
创建一个字典
alien_0 = {'color': 'green', 'points': 5}
print(alien_0)
{'color': 'green', 'points': 5}
访问字典中的值
alien_0 = {'color': 'green', 'points': 5}
print(alien_0['color'])
print(alien_0['points'])
green 5
添加键-值对
alien_0 = {'color': 'green', 'points': 5}
print(alien_0)
{'color': 'green', 'points': 5}alien_0['x_position'] = 0
alien_0['y_position'] = 25
print(alien_0)
{'color': 'green', 'points': 5, 'x_position': 0, 'y_position': 25}
修改字典中的值
alien_0 = {'color': 'green', 'points': 5}
print(alien_0)
alien_0['x_position'] = 0
alien_0['y_position'] = 25
print(alien_0)
alien_0['y_position'] = 180
print(alien_0)
{'color': 'green', 'points': 5} {'color': 'green', 'points': 5, 'x_position': 0, 'y_position': 25} {'color': 'green', 'points': 5, 'x_position': 0, 'y_position': 180}
删除键-值对
alien_0 = {'color': 'green', 'points': 5}
print(alien_0)
alien_0['x_position'] = 0
alien_0['y_position'] = 25
print(alien_0)
alien_0['y_position'] = 180
print(alien_0)
del alien_0['color']
print(alien_0)
{'color': 'green', 'points': 5} {'color': 'green', 'points': 5, 'x_position': 0, 'y_position': 25} {'color': 'green', 'points': 5, 'x_position': 0, 'y_position': 180} {'points': 5, 'x_position': 0, 'y_position': 180}
注意：删除键-值对永远消失！！！
由类似对象组成的字典
Python 字典.items() 方法以列表返回可遍历的(键, 值) 列表。
favorite_languages.items()
Python 字典.keys() 方法以列表返回可遍历的(键) 列表。
favorite_languages.keys()
Python 字典.values() 方法以列表返回可遍历的(值) 列表。
favorite_languages.values()
Python sorted(字典.values()) 按顺序方法以列表返回可遍历的(值) 列表。
sorted(favorite_languages.values)
Python set(字典.values()) 列表去重方法以列表返回可遍历的(值) 无重复值列表。
set(favorite_languages.values)
favorite_languages = {
'jen': 'python',
'sarah': 'c',
'edward': 'ruby',
'phil': 'python',
}
for name, language in favorite_languages.items():
print("%s's favorite language is %s ." %(name.title(),language.title()))Jen's favorite language is Python . Sarah's favorite language is C . Edward's favorite language is Ruby . Phil's favorite language is Python .
嵌套
字典列表
# Make an empty list for storing aliens.创建空字典
aliens = []
# Make 30 green aliens.添加字典列表
for alien_number in range (0,30):
if alien_number > 3 and alien_number < 6 :
new_alien = {'color': 'yellow', 'points': 5, 'speed': 'slow'}
aliens.append(new_alien)
else:
new_alien = {'color': 'green', 'points': 5, 'speed': 'slow'}
aliens.append(new_alien)
print('====>>:%s'%(alien_number))
print(len(aliens))
#修改外星人战斗力
for alien in aliens[0:6]:
#颜色green的移动速度10
if alien['color'] == 'green':
alien['color'] = 'yellow'
alien['speed'] = 'medium'
alien['points'] = 10
#颜色red移动速度15
elif alien['color'] == 'yellow':
alien['color'] = 'red'
alien['speed'] = 'fast'
alien['points'] = 15
# Show the first 5 aliens:
for alien in aliens[0:7]:
print(alien)
print结果
====>>:0
...
====>>:29
30
{'color': 'yellow', 'points': 10, 'speed': 'medium'}
{'color': 'yellow', 'points': 10, 'speed': 'medium'}
{'color': 'yellow', 'points': 10, 'speed': 'medium'}
{'color': 'yellow', 'points': 10, 'speed': 'medium'}
{'color': 'red', 'points': 15, 'speed': 'fast'}
{'color': 'red', 'points': 15, 'speed': 'fast'}
{'color': 'green', 'points': 5, 'speed': 'slow'}
...字典中存储列表
# Store information about a pizza being ordered.
#存储所点披萨的信息
pizza = {
'crust': 'thick',
'toppings': ['mushrooms', 'extra cheese'],
}
# Summarize the order.
#概述披萨信息
print("You ordered a %s-crust pizza with the following toppings:" %(pizza['crust']))
for topping in pizza['toppings']:
print(" %s"%(topping))
#执行结果
You ordered a thick-crust pizza with the following toppings:
mushrooms
extra cheese字典中存储字典
users = {'aeinstein': {'first': 'albert',
'last': 'einstein',
'location': 'princeton'},
'mcurie': {'first': 'marie',
'last': 'curie',
'location': 'paris'},
}
for username, user_info in users.items():
print("
Username: " + username)
full_name = user_info['first'] + " " + user_info['last']
location = user_info['location']
print(" Full name: " + full_name.title())
print(" Location: " + location.title())
#执行结果
Username: aeinstein
Full name: Albert Einstein
Location: Princeton
Username: mcurie
Full name: Marie Curie
Location: Paris