Chemical & Biological Engineering CBE Computational Turbulent Reacting Flow CTRFlow

Publications Calendar Research Teaching Zoom LDS

Publications Calendar Research Teaching Zoom LDS

JSON files

• It is common to store data in a file in a format that is easy to read, both for people and machines.
• One such format is JSON.
• This has many uses, but a common one is to store user variables that control how a code is run, without having to change the code itself, only the input file.
• JSON files make use of key-value pairs, like dictionaries.
  • values can be numbers, strings, arrays, true/false, null, or dictionaries (called objects), also null.
  • Don't forget to end lines with commas, except for the last element in an object.
• Here's a very short tutorial

Example file

%pycat input.json

{
"Ldomain":  0.01,
"Li":       0.01,
"k":        1.0,
"nu":       1.5E-5,
"tRun":     0.1,
"N_eta":    10.76,
"C_lambda": 15,
"dtFactor": 0.5,
"dtWrite":  0.001,
"doRxn":    false,
"Tbounds":  [300, 2500],
"mech":     null,

"thermo": {
    "mech": "gri30.yaml",
    "P":    101325,
    "T0":   300,
    "X0":   "O2:1, N2:7.52",
    "T1":   300,
    "X1":   "CH4:1"
},

"Vars": {
    "scal": {
        "D": 2.24E-5,
        "BC": {
            "loType": "D",
            "hiType": "D",
            "lo":     0.0,
            "hi":     1.0
        }
    },
    "ygas": {
        "BC": {
            "loType": "D",
            "hiType": "D"
        }
    },
    "enth": {
        "BC": {
            "loType": "D",
            "hiType": "D"
        }
    }
}
}

Read data from a JSON file

import json

with open("input.json", "r") as ifile:
    data = json.load(ifile)

data.keys()

# access data in the file using dictionary syntax:

Ldomain  = data["Ldomain"]
rxns     = data["doRxn"]
scalBClo = data["Vars"]["scal"]["BC"]["lo"]