Convert JSON schema to BigQuery schema

json_schema_to_bq_schema.py

import json
import sys

f = sys.argv[1]
bq_schema = []

def tree_to_schema(tree):
    schema = []
    properties = tree['properties']
    for a in properties:
        row = {'name': a}
        vals = properties[a]
        data_type = vals['type']
        if vals['type'] == 'object':
            data_type = 'record'
            row['fields'] = tree_to_schema(vals)

        if vals['type'] == 'array':
            mode = 'repeated'      
            data_type = vals['items']['type']  
        elif a in data['required']:
            mode = 'required'
        else:
            mode = 'nullable'
        if type(data_type) is list:
            data_type.remove('null')
            if len(data_type) == 1:
                data_type = data_type[0]
            else:
                raise Exception('Unhandled schema error','Multiple types')
        if data_type == 'null':
            # Choose another data type for a field that is always null
            data_type = 'string'
        row['type'] = data_type
        row['mode'] = mode
        schema.append(row)
    return schema

with open(f) as json_file:
    data = json.load(json_file)
    bq_schema = tree_to_schema(data)
    print(json.dumps(bq_schema))