I have .json files in the following format:

{
    "uls":{
        "equ1-L1-u": {"D": 1.10, "La": 1.50, "Lb": 1.50},
        "equ1-L2-u": {"D": 1.10, "La": 1.50, "Lb": 1.50},
    },
    "sls":{
        "cha-L1": {"Ld": 1.00, "Le": 1.00, "Lf": 1.00, "Lg": 1.00, "Lh": 1.00},
        "cha-L2": {"D": 1.00, "Df": 1.00},
    }
}

which I want to convert to CSV “database” style format:

Criteria,  Name,         D,    Df,   La,    Lb,     Ld,   Le,   Lf,   Lg,   Lh  
uls,       equ1-L1-u,    1.10,     , 1.50,  1.50,     ,     ,     ,     ,    
uls,       equ1-L2-u,    1.10,     , 1.50,  1.50,     ,     ,     ,     ,    
sls,       cha-L1,           ,     ,     ,      ,1.00 , 1.00, 1.00, 1.00, 1.00      
sls,       cha-L2,       1.00, 1.00,     ,      ,     ,     ,     ,     ,

Ideally, I would not have to define the value keys beforehand, but for now I’m fine doing it if needed.

Here’s what I got now, it’s working for this specific case of 2 level of nesting. I’m able to do make it work for 3 or 4 levels of nesting by modifying the code, but ideally the same code could be used for all levels of nesting (maybe recursion?).

# Function to convert json objects to csv
import json
import csv

def make_csv_dict(data, key_headers):
    csv_dict = []
    for i in data:
        for j in data[i]:
            csv_dict.append({
                key_headers[0]: i,
                key_headers[1]: j,
                **data[i][j]
                })
    return csv_dict

### ENTER DATA HERE ###
key_headers = ["Criteria", "Name"]
path = "File.json"
### ENTER DATA HERE ###

# Read json
with open(path) as json_file:
    data = json.load(json_file)

# make csv_dict from .json data
csv_dict = make_csv_dict(data, key_headers)

# writing to csv file
fieldnames = ["Criteria", "Name", "D", "Df", "La", "Lb", "Lc", "Ld", "Le", "Lf", "Lg", "Lh", "Sl", "Sh", "W", "T", "A", "E"]

with open(path.replace(".json",".csv"), 'w', newline="") as f:
    writer = csv.DictWriter(f, fieldnames)
    writer.writeheader()
    writer.writerows(csv_dict)