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data_1=pd.DataFrame({'food':['bacon火腿','sausage红肠','pulled pork手撕肉','sirloin牛里脊肉','beef jerky牛肉干','mutton shashlik烤羊肉串','Chicken salad鸡肉','Minced chicken鸡肉泥','dried squids鱿鱼干','dried fish鱼干','sausage红肠','bacon火腿','sausage红肠','bacon火腿','Chicken salad鸡肉','dried squids鱿鱼干','dried fish鱼干','mutton shashlik烤羊肉串','beef jerky牛肉干','Minced chicken鸡肉泥','pulled pork手撕肉','sirloin牛里脊肉','mutton shashlik烤羊肉串','Chicken salad鸡肉','Minced chicken鸡肉泥','bacon火腿','sausage红肠','pulled pork手撕肉','sirloin牛里脊肉','beef jerky牛肉干','mutton shashlik烤羊肉串','Chicken salad鸡肉','Minced chicken鸡肉泥','dried squids鱿鱼干','dried fish鱼干','sausage红肠','bacon火腿','sausage红肠','bacon火腿','Chicken salad鸡肉','dried squids鱿鱼干','dried fish鱼干','mutton shashlik烤羊肉串','beef jerky牛肉干','sirloin牛里脊肉','mutton shashlik烤羊肉串','Chicken salad鸡肉','Minced chicken鸡肉泥'],'weight(g)':abs((np.random.normal(0,1,size=48)*24+10)).astype(np.int32)})
print(data_1)
food weight(g)
0 bacon火腿 47
1 sausage红肠 48
2 pulled pork手撕肉 5
3 sirloin牛里脊肉 21
4 beef jerky牛肉干 35
5 mutton shashlik烤羊肉串 23
6 Chicken salad鸡肉 11
7 Minced chicken鸡肉泥 8
8 dried squids鱿鱼干 3
9 dried fish鱼干 13
10 sausage红肠 20
11 bacon火腿 26
12 sausage红肠 5
13 bacon火腿 10
14 Chicken salad鸡肉 31
15 dried squids鱿鱼干 19
16 dried fish鱼干 4
17 mutton shashlik烤羊肉串 4
18 beef jerky牛肉干 18
19 Minced chicken鸡肉泥 21
20 pulled pork手撕肉 6
21 sirloin牛里脊肉 6
22 mutton shashlik烤羊肉串 0
23 Chicken salad鸡肉 17
24 Minced chicken鸡肉泥 46
25 bacon火腿 22
26 sausage红肠 4
27 pulled pork手撕肉 2
28 sirloin牛里脊肉 4
29 beef jerky牛肉干 67
30 mutton shashlik烤羊肉串 3
31 Chicken salad鸡肉 15
32 Minced chicken鸡肉泥 43
33 dried squids鱿鱼干 3
34 dried fish鱼干 10
35 sausage红肠 42
36 bacon火腿 35
37 sausage红肠 5
38 bacon火腿 2
39 Chicken salad鸡肉 18
40 dried squids鱿鱼干 0
41 dried fish鱼干 19
42 mutton shashlik烤羊肉串 4
43 beef jerky牛肉干 20
44 sirloin牛里脊肉 38
45 mutton shashlik烤羊肉串 14
46 Chicken salad鸡肉 1
47 Minced chicken鸡肉泥 46
发现数据框‘food’列中有很多重复。如果我们给数据假如新列，并要求新列与food存在某种逻辑关系。例如给‘food’标记食材来源。
通过map函数可以很轻松实现上面的要求。
map的实质是把一种映射法则应用到所制定的列上，比如这里的‘food’列。这种映射法则通常通过字典与函数来体现。即map(lambda x:meat_source[x]
即从food列中取值与meat_source的键对应，返回该键对应的值，animal的值即为对应的值
DataFrame中对应的是applymap()函数，DataFrame还有apply()函数
meat_source={'bacon火腿':'猪','sausage红肠':'猪','pulled pork手撕肉':'猪','sirloin牛里脊肉':'牛','beef jerky牛肉干':'牛','mutton shashlik烤羊肉串':'羊','chicken salad鸡肉':'鸡','minced chicken鸡肉泥':'鸡','dried squids鱿鱼干':'鱿鱼','dried fish鱼干':'鱼'}
data_1['animal']=data_1['food'].map(meat_source)
print(data_1)
food weight(g) animal
0 bacon火腿 47 猪
1 sausage红肠 48 猪
2 pulled pork手撕肉 5 猪
3 sirloin牛里脊肉 21 牛
4 beef jerky牛肉干 35 牛
5 mutton shashlik烤羊肉串 23 羊
6 Chicken salad鸡肉 11 NaN
7 Minced chicken鸡肉泥 8 NaN
8 dried squids鱿鱼干 3 鱿鱼
9 dried fish鱼干 13 鱼
10 sausage红肠 20 猪
11 bacon火腿 26 猪
12 sausage红肠 5 猪
13 bacon火腿 10 猪
14 Chicken salad鸡肉 31 NaN
15 dried squids鱿鱼干 19 鱿鱼
16 dried fish鱼干 4 鱼
17 mutton shashlik烤羊肉串 4 羊
18 beef jerky牛肉干 18 牛
19 Minced chicken鸡肉泥 21 NaN
20 pulled pork手撕肉 6 猪
21 sirloin牛里脊肉 6 牛
22 mutton shashlik烤羊肉串 0 羊
23 Chicken salad鸡肉 17 NaN
24 Minced chicken鸡肉泥 46 NaN
25 bacon火腿 22 猪
26 sausage红肠 4 猪
27 pulled pork手撕肉 2 猪
28 sirloin牛里脊肉 4 牛
29 beef jerky牛肉干 67 牛
30 mutton shashlik烤羊肉串 3 羊
31 Chicken salad鸡肉 15 NaN
32 Minced chicken鸡肉泥 43 NaN
33 dried squids鱿鱼干 3 鱿鱼
34 dried fish鱼干 10 鱼
35 sausage红肠 42 猪
36 bacon火腿 35 猪
37 sausage红肠 5 猪
38 bacon火腿 2 猪
39 Chicken salad鸡肉 18 NaN
40 dried squids鱿鱼干 0 鱿鱼
41 dried fish鱼干 19 鱼
42 mutton shashlik烤羊肉串 4 羊
43 beef jerky牛肉干 20 牛
44 sirloin牛里脊肉 38 牛
45 mutton shashlik烤羊肉串 14 羊
46 Chicken salad鸡肉 1 NaN
47 Minced chicken鸡肉泥 46 NaN
发现‘animal’列有空值。原因是meat_source中的键与‘food’列值不完全一致。
通过map(str.lower)把food列中的值的第一个字母转变成小写，这样meat_source中的键与‘food’列值完全一致，这样Nan会自动消失。
data_1['animal']=data_1['food'].map(str.lower).map(meat_source)
或data_1['animal']=data_1['food'].map(lambda x:meat_source[x.lower()])
print(data_1)
food weight(g) animal
0 bacon火腿 47 猪
1 sausage红肠 48 猪
2 pulled pork手撕肉 5 猪
3 sirloin牛里脊肉 21 牛
4 beef jerky牛肉干 35 牛
5 mutton shashlik烤羊肉串 23 羊
6 Chicken salad鸡肉 11 鸡
7 Minced chicken鸡肉泥 8 鸡
8 dried squids鱿鱼干 3 鱿鱼
9 dried fish鱼干 13 鱼
10 sausage红肠 20 猪
11 bacon火腿 26 猪
12 sausage红肠 5 猪
13 bacon火腿 10 猪
14 Chicken salad鸡肉 31 鸡
15 dried squids鱿鱼干 19 鱿鱼
16 dried fish鱼干 4 鱼
17 mutton shashlik烤羊肉串 4 羊
18 beef jerky牛肉干 18 牛
19 Minced chicken鸡肉泥 21 鸡
20 pulled pork手撕肉 6 猪
21 sirloin牛里脊肉 6 牛
22 mutton shashlik烤羊肉串 0 羊
23 Chicken salad鸡肉 17 鸡
24 Minced chicken鸡肉泥 46 鸡
25 bacon火腿 22 猪
26 sausage红肠 4 猪
27 pulled pork手撕肉 2 猪
28 sirloin牛里脊肉 4 牛
29 beef jerky牛肉干 67 牛
30 mutton shashlik烤羊肉串 3 羊
31 Chicken salad鸡肉 15 鸡
32 Minced chicken鸡肉泥 43 鸡
33 dried squids鱿鱼干 3 鱿鱼
34 dried fish鱼干 10 鱼
35 sausage红肠 42 猪
36 bacon火腿 35 猪
37 sausage红肠 5 猪
38 bacon火腿 2 猪
39 Chicken salad鸡肉 18 鸡
40 dried squids鱿鱼干 0 鱿鱼
41 dried fish鱼干 19 鱼
42 mutton shashlik烤羊肉串 4 羊
43 beef jerky牛肉干 20 牛
44 sirloin牛里脊肉 38 牛
45 mutton shashlik烤羊肉串 14 羊
46 Chicken salad鸡肉 1 鸡
47 Minced chicken鸡肉泥 46 鸡
添加amount=weigh×price项，看看就行，不懂也罢
product=['bacon火腿','sausage红肠','pulled pork手撕肉','sirloin牛里脊肉','beef jerky牛肉干','mutton shashlik烤羊肉串',
'Chicken salad鸡肉','Minced chicken鸡肉泥','dried squids鱿鱼干','dried fish鱼干']
price=[1,1.5,2,2.3,2.6,3.6,2,2.6,8,9.9]
get_Data={k:p*i for i,k in zip(list(data_1['weight(g)'].values),range(len(data_1['weight(g)'])))\
for m,p in zip(product,price)\
if m==data_1['food'][k]}
data_1['amount']=data_1.index.map(get_Data)
print(data_1.reindex(columns=['food','weight(g)','animal','amount']))
food weight(g) animal amount
0 bacon火腿 47 猪 47.0
1 sausage红肠 48 猪 72.0
2 pulled pork手撕肉 5 猪 10.0
3 sirloin牛里脊肉 21 牛 48.3
4 beef jerky牛肉干 35 牛 91.0
5 mutton shashlik烤羊肉串 23 羊 82.8
6 Chicken salad鸡肉 11 鸡 22.0
7 Minced chicken鸡肉泥 8 鸡 20.8
8 dried squids鱿鱼干 3 鱿鱼 24.0
9 dried fish鱼干 13 鱼 128.7
10 sausage红肠 20 猪 30.0
11 bacon火腿 26 猪 26.0
12 sausage红肠 5 猪 7.5
13 bacon火腿 10 猪 10.0
14 Chicken salad鸡肉 31 鸡 62.0
15 dried squids鱿鱼干 19 鱿鱼 152.0
16 dried fish鱼干 4 鱼 39.6
17 mutton shashlik烤羊肉串 4 羊 14.4
18 beef jerky牛肉干 18 牛 46.8
19 Minced chicken鸡肉泥 21 鸡 54.6
20 pulled pork手撕肉 6 猪 12.0
21 sirloin牛里脊肉 6 牛 13.8
22 mutton shashlik烤羊肉串 0 羊 0.0
23 Chicken salad鸡肉 17 鸡 34.0
24 Minced chicken鸡肉泥 46 鸡 119.6
25 bacon火腿 22 猪 22.0
26 sausage红肠 4 猪 6.0
27 pulled pork手撕肉 2 猪 4.0
28 sirloin牛里脊肉 4 牛 9.2
29 beef jerky牛肉干 67 牛 174.2
30 mutton shashlik烤羊肉串 3 羊 10.8
31 Chicken salad鸡肉 15 鸡 30.0
32 Minced chicken鸡肉泥 43 鸡 111.8
33 dried squids鱿鱼干 3 鱿鱼 24.0
34 dried fish鱼干 10 鱼 99.0
35 sausage红肠 42 猪 63.0
36 bacon火腿 35 猪 35.0
37 sausage红肠 5 猪 7.5
38 bacon火腿 2 猪 2.0
39 Chicken salad鸡肉 18 鸡 36.0
40 dried squids鱿鱼干 0 鱿鱼 0.0
41 dried fish鱼干 19 鱼 188.1
42 mutton shashlik烤羊肉串 4 羊 14.4
43 beef jerky牛肉干 20 牛 52.0
44 sirloin牛里脊肉 38 牛 87.4
45 mutton shashlik烤羊肉串 14 羊 50.4
46 Chicken salad鸡肉 1 鸡 2.0
47 Minced chicken鸡肉泥 46 鸡 119.6
