将字典列表与 pandas 系列进行比较并根据匹配填充字典

Question

I have a list of dicts that I want to populate by updating the dict if a match of several values within a dict is found in a pandas series. eg

lis_of_dicts = [{'A':'a', 'B':'b','C':'c', 'D':'d'},
                {'A':'1', 'B':'2','C':'3','D':'4'}, 
                {'A':'M','B':'N','C':'O','D':'P'}]

dd = {'col1':['b', 'M'], 'col2':['d','P'], 'col3':['7.5','29']}
df = pd.Dataframe(dd, columns = ['col1', 'col2', 'col3']) 
pd_series = pd.Series(tuple(value) for value in df.values), index=df.index)

which generated:

0 (b, d, 7.5)
1 (M, P, 29)

Desired result:

[{'A':'a', 'B':'b','C':'c', 'val': '7.5','D':'d'}, 
 {'A':'1', 'B':'2','C':'3', 'val':'NA', 'D':'4'}, 
 {'A':'M','B':'N','C':'O','val':'29','D':'P'}]

I tried this but I could not even get the match so could not proceed:

for i in pd_series:
    for x in lis_of_dicts:
        if [x[key] == i[0] in x and [x[key] == i[1] in x for key in x]:
            x.update({'val':'i[2]'})
        else:
            x.update({'val':'NA'})

I am unable to generate any result. Notice the order of the dict should remain the same except for the value been added should be before the last item in the dictionary.

Answer 1

I would go for a nested loop based solution:

>>> df_2 = pd.DataFrame(lis_of_dicts)
>>> df_2
   A  B  C  D
0  a  b  c  d
1  1  2  3  4
2  M  N  O  P
>>> cols = df_2.columns
>>> for ix, row in df_2.iterrows():
...     for item in pd_series:
...         if set(row[cols]) & set(item):
...             df_2.loc[ix, 'val'] = item[2]
...             break
...     else:
...         df_2.loc[ix, 'val'] = 'NA'

>>> df_2.to_dict('r')
[{'A': 'a', 'B': 'b', 'C': 'c', 'D': 'd', 'val': 7.5},
 {'A': '1', 'B': '2', 'C': '3', 'D': '4', 'val': 'NA'},
 {'A': 'M', 'B': 'N', 'C': 'O', 'D': 'P', 'val': 29}]

EDIT : It can be simplified, as follows:

output = []
for d in lis_of_dicts:
    for item in pd_series:
        if set(d.values()) & set(item):
            d['val'] = item[2]
            break
    else:
        d['val'] = 'NA'
    output.append(d)
>>> output
[{'A': 'a', 'B': 'b', 'C': 'c', 'D': 'd', 'val': 7.5},
 {'A': '1', 'B': '2', 'C': '3', 'D': '4', 'val': 'NA'},
 {'A': 'M', 'B': 'N', 'C': 'O', 'D': 'P', 'val': 29}]

EDIT 2 :

NOTE: This will only reliably work in python version >= 3.7, as order is not guaranteed to be maintained in dict s for lower versions.

To place val in 2nd last element:

output = []
for d in lis_of_dicts:
    last = d.popitem()
    for item in pd_series:
        if set(d.values()) & set(item):
            d['val'] = item[2]
            d.update([last])
            break
    else:
        d['val'] = 'NA'
        d.update([last])
    output.append(d)

>>> output
[{'A': 'a', 'B': 'b', 'C': 'c', 'val': 7.5, 'D': 'd'},
 {'A': '1', 'B': '2', 'C': '3', 'val': 'NA', 'D': '4'},
 {'A': 'M', 'B': 'N', 'C': 'O', 'val': 29, 'D': 'P'}]