问题：书上P413页中缺少一部分代码，否则无法做下面的分析
解决思路：根据书中提示，先建立一个空表，再对每个二层数据提取后连接在一起，不过我这里没有使用concat
代码如下：
nutrients = pd.DataFrame()
for i in range(0,len(db)):
summrize=pd.DataFrame(db[i]['nutrients'],columns=['description','group','units','value','id'])
summrize['id']=db[i]['id']
nutrients = nutrients.append(summrize)
nutrients
注意，行号虽然显示奇怪，但数据都在且无问题，但需要运行7分钟左右
| | description | group | units | value | id |
|---|
| 0 |
Protein |
Composition |
g |
25.180 |
1008 |
|---|
| 1 |
Total lipid (fat) |
Composition |
g |
29.200 |
1008 |
|---|
| 2 |
Carbohydrate, by difference |
Composition |
g |
3.060 |
1008 |
|---|
| 3 |
Ash |
Other |
g |
3.280 |
1008 |
|---|
| 4 |
Energy |
Energy |
kcal |
376.000 |
1008 |
|---|
| ... |
... |
... |
... |
... |
... |
|---|
| 45 |
Vitamin B-12, added |
Vitamins |
mcg |
0.000 |
43546 |
|---|
| 46 |
Cholesterol |
Other |
mg |
0.000 |
43546 |
|---|
| 47 |
Fatty acids, total saturated |
Other |
g |
0.072 |
43546 |
|---|
| 48 |
Fatty acids, total monounsaturated |
Other |
g |
0.028 |
43546 |
|---|
| 49 |
Fatty acids, total polyunsaturated |
Other |
g |
0.041 |
43546 |
|---|
389355 rows × 5 columns