Python基础三【字典】

#字典，键-值对，{}表示; 字典项不排序；可以用任意值做为键；
import operator
import pprint
myCat={'size':'fat','color':'gray','disposition':'loud'}
print(myCat['color'])#gray

myCat={3:'fat',10:'gray',5:'loud'}
print(myCat[3])#fat

print(myCat)
for v in myCat.values():#获取字典键列表
    print(v)
for v in myCat.keys():#获取字典值列表
    print(v)
for v in myCat.items():#获取字典项列表
    print(v)#(3, 'fat')  (10, 'gray')   (5, 'loud')

for key,v in myCat.items():#获取字典项列表（多重赋值）
    print('key:'+str(key)+'  value:'+str(v))#key:3  value:fat   key:10  value:gray   key:5  value:loud

#检查字典中是否存在键或值  in, not in
print(3 in myCat.keys())#True
print(7 not in myCat.keys())#True
print(33 in myCat.keys())#False

#设置默认值setDefault()
myCat.setdefault(33,'maomao')#如果不存在33键，则设置33键及‘maomao’值；否则返回33对应值
print(myCat)#{3: 'fat', 10: 'gray', 5: 'loud', 33: 'maomao'}
print(myCat[10])#gray
print(myCat[3])#fat

print(myCat.setdefault(3,'maomao'))#直接返回的  fat ，因为有  3 键

print('Part2------------------------------')

#客人带东西
allGuests = {'Alice': {'apples': 5, 'pretzels': 12},
'Bob': {'ham sandwiches': 3, 'apples': 2},
'Carol': {'cups': 3, 'apple pies': 1}}

def totalBrought(guests, item):
    numBrought = 0
    for k, v in guests.items():
        numBrought = numBrought + v.get(item, 0)
    return numBrought

print('Number of things being brought:')
print(' - Apples ' + str(totalBrought(allGuests, 'apples')))
print(' - Cups ' + str(totalBrought(allGuests, 'cups')))
print(' - Cakes ' + str(totalBrought(allGuests, 'cakes')))
print(' - Ham Sandwiches ' + str(totalBrought(allGuests, 'ham sandwiches')))
print(' - Apple Pies ' + str(totalBrought(allGuests, 'apple pies')))