Validating new entries' zip codes in mysql table?

I'm trying to validate new entries in a MySQL table by sending a GET request to the ZipCodeAPI (http://www.zipcodeapi.com/API). The API returns a json if the entry is valid. For new entries being inserted into the table, the API should verify that the entry in the postal_code column is valid. How would I allow the API to take in any possible zip code from the column postal_code in the table? Also, how would I test if the json is valid? Is there a function I could call that would determine if a json object is returned?

The code is in Python.

import requests
import mysql.connector
import json
dbconnect= mysql.connector.connect(user= 'root', database= 'contacts')
cursor = dbconnect.cursor()
url= "http://www.zipcodeapi.com/rest/QPIGMAfa0CmeyWWp0bum6rk3K6jdhK57zOOmo3xpFTDeQzERL8dRAyVlEeyWYE3x/info.json/06226/degrees"
response= requests.get(url)

data= jsonloads(response.content)
query= cursor.execute("INSERT INTO customer "
              "(id, ContactHash, NewContactHash, name, address1, address2, address3, city, country_code, country_code_iso2, state_province, postal_code, email_address, status, phone, CardCode, created_at, updated_at) 
              "VALUES (%d, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s)")

rows= cursor.fetchall()
for row in rows:
  json= response.json()
  if (json):
    print json
  else:
    print "Invalid zip code. Please try again."