Convert a JSON file to a Swagger Definition

json-to-swagger-definition.py

import sys
import json

def eexit(message):
    """Print a message and exit."""
    print(message)
    exit(1)

def convert(inFile, outFile):
    """Convert the JSON file to swagger YAML."""
    data = None
    with open(inFile, 'r') as fin:
        data = json.loads(fin.read())
    if not data:
        eexit("Could not import JSON.")
    with open(outFile, 'w') as fout:
        outDict(data, fout, 0)

def outDict(obj, fout, indent):
    """Convert the dictionary at the given indentation level."""
    for k in sorted(obj):
        fout.write('  '*indent+k+':\n')
        outType(obj[k], fout, indent+1)

def outType(v, fout, indent):
    """Convert the object at the given indentation level."""
    if type(v) is dict:
        fout.write('  '*indent+'type: object\n')
        fout.write('  '*indent+'properties:\n')
        outDict(v, fout, indent+1)
    elif type(v) is float:
        fout.write('  '*indent+'type: number\n')
        fout.write('  '*indent+'format: double\n')
    elif type(v) is int:
        fout.write('  '*indent+'type: number\n')
        fout.write('  '*indent+'format: int32\n')
    elif type(v) is unicode:
        fout.write('  '*indent+'type: string\n')
    elif type(v) is list:
        fout.write('  '*indent+'type: array\n')
        fout.write('  '*indent+'items:\n')
        if len(v) > 0:
            outType(v[0], fout, indent+1)
        else:
            outType(None, fout, indent+1)
    elif type(v) is bool:
        fout.write('  '*indent+'type: boolean\n')
    elif v is None:
        fout.write('  '*indent+'type: object\n')
    else:
        eexit('No handling for: '+str(type(v)))

if __name__ == "__main__":
    if len(sys.argv) <= 1:
        eexit("Input file required.")
    elif len(sys.argv) <= 2:
        eexit("Output file requried.")
    convert(sys.argv[1], sys.argv[2])

It's common for me to be asked to create a swagger document for an API after the API has been written. Sometimes the responses can be large and typing the definition by hand is consuming.

This script will take a JSON file and convert it to a swagger definition.

It does not add descriptions. It does not add endpoint information. It does not do anything fancy except create the definition for you.