open a .json file with multiple dictionaries

Question

I have a problem that I can't solve with python, it is probably very stupid but I didn't manage to find the solution by myself.

I have a .json file where the results of a simulation are stored. The result is stored as a series of dictionaries like

{"F_t_in_max": 709.1800264942982, "F_t_out_max": 3333.1574129603068, "P_elec_max": 0.87088836042046958, "beta_max": 0.38091242406098391, "r0_max": 187.55175182942901, "r1_max": 1354.8636763521174, " speed ": 8}
{"F_t_in_max": 525.61428305710433, "F_t_out_max": 2965.0538075438467, "P_elec_max": 0.80977406754203796, "beta_max": 0.59471606595464666, "r0_max": 241.25371753877008, "r1_max": 688.61786996066826, " speed ": 9}
{"F_t_in_max": 453.71124051199763, "F_t_out_max": 2630.1763649193008, "P_elec_max": 0.64268078173342935, "beta_max": 1.0352896471221695, "r0_max": 249.32706230502498, "r1_max": 709.11415981343885, " speed ": 10}

I would like to open the file and and access the values like to plot "r0_max" as function of "speed" but I can't open unless there is only one dictionary. I use

with open('./results/rigid_wing_opt.json') as data_file:    
    data = json.load(data_file) 

but When the file contains more than one dictionary I get the error

ValueError: Extra data: line 5 column 1 - line 6 column 1 (char 217 - 431)

Answer 1

If your input data is exactly as provided then you should be able to interpret each individual dictionary using json.load. If each dictionary is on its own line then this should be sufficient:

with open('filename', 'r') as handle:
    json_data = [json.loads(line) for line in handle]

Answer 2

I would recommend reading the file line-by-line and convert each line independently to a dictionary.

You can place each line into a list with the following code:

import ast
# Read all lines into a list
with open(fname) as f:
    content = f.readlines()

# Convert each list item to a dict
content = [ ast.literal_eval( line ) for line in content ]

Or an even shorter version performing the list comprehension on the same line:

import ast
# Read all lines into a list
with open(fname) as f:
    content = [ ast.literal_eval( l ) for l in f.readlines() ]