How to de-nested a list of list of dictionary into a DataFrame?

First, convert strings to dictionary.

import pandas as pd
import json

example_data=['[{"date_update":"31-03-2022","diemquatrinh":"6.0"}]',  

'[{"date_update":"28-04-2022","diemquatrinh":"6.5"}]', 

'[{"date_update":"25-12-2021","diemquatrinh":"6.0"}, {"date_update":"28-04-2022","diemquatrinh":"6.25"},{"date_update":"28-07-2022","diemquatrinh":"6.5"}]',

'[{"date_update":null,"diemquatrinh":null}]']

listt=[]
for i in example_data:
    listt.append(json.loads(i))

when i examine the data, each dictionary has the same keys. This means I can collect all dictionaries in one list.

main_list = [item for sublist in listt for item in sublist]
print(main_list)
'''
[{'date_update': '31-03-2022', 'diemquatrinh': '6.0'}, {'date_update': '28-04-2022', 'diemquatrinh': '6.5'}, {'date_update': '25-12-2021', 'diemquatrinh': '6.0'}, {'date_update': '28-04-2022', 'diemquatrinh': '6.25'}, {'date_update': '28-07-2022', 'diemquatrinh': '6.5'}, {'date_update': None, 'diemquatrinh': None}]
'''

All that’s left is to convert the list to a dataframe:

df=pd.DataFrame(main_list)
print(df)
'''
    date_update diemquatrinh
0   31-03-2022  6.0
1   28-04-2022  6.5
2   25-12-2021  6.0
3   28-04-2022  6.25
4   28-07-2022  6.5
5   None        None

'''