Calling a JSON API Using Python – Step-by-Step Guide with Example

Calling a JSON API Using Python (Retrieve Google Place ID)

In this assignment, we will create a Python program that communicates with a web service, retrieves JSON data, and extracts information from it.

The program works similarly to the example provided at:

👉 http://www.py4e.com/code3/geojson.py

The application will:

✅ Prompt the user for a location
✅ Call a web API using that location
✅ Retrieve JSON data from the service
✅ Parse the JSON response
✅ Extract location details such as latitude, longitude, and formatted address

A Place ID is a unique textual identifier used by Google Maps to identify a specific location.

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🌐 API Endpoint

For this assignment, use the following testing API (a static subset of Google data):

http://py4e-data.dr-chuck.net/json?

Important Notes

• Uses the same address parameter as the Google API
• No rate limit (safe for testing)
• Requires a key parameter
• Address must be URL encoded using urllib.parse.urlencode()

If you open the URL without parameters, you will see:

No address...

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🧠 Program Workflow

1. Ask user to enter a location
2. Build API request URL
3. Send request to web service
4. Receive JSON response
5. Convert JSON text into Python dictionary
6. Extract required data

Step-by-step infographic showing how Python retrieves and parses JSON data from a web API

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🐍 Python Solution

import urllib.request
import urllib.parse
import urllib.error
import json
import ssl

# API Key setup
api_key = False

# If you have a real Google API key, place it here
# api_key = 'AIzaSyXXXX'

if api_key is False:
    api_key = 42
    serviceurl = 'http://py4e-data.dr-chuck.net/json?'
else:
    serviceurl = 'https://maps.googleapis.com/maps/api/geocode/json?'

# Ignore SSL certificate errors
ctx = ssl.create_default_context()
ctx.check_hostname = False
ctx.verify_mode = ssl.CERT_NONE

while True:
    address = input('Enter location: ')
    if len(address) < 1:
        break

    # Create parameters dictionary
    parms = dict()
    parms['address'] = address
    if api_key is not False:
        parms['key'] = api_key

    # Encode parameters into URL
    url = serviceurl + urllib.parse.urlencode(parms)

    print('Retrieving:', url)

    # Open URL and read data
    uh = urllib.request.urlopen(url, context=ctx)
    data = uh.read().decode()
    print('Retrieved', len(data), 'characters')

    # Convert JSON text to dictionary
    try:
        js = json.loads(data)
    except:
        js = None

    # Error handling
    if not js or 'status' not in js or js['status'] != 'OK':
        print('==== Failure To Retrieve ====')
        print(data)
        continue

    # Pretty print JSON
    print(json.dumps(js, indent=4))

    # Extract required data
    lat = js['results'][0]['geometry']['location']['lat']
    lng = js['results'][0]['geometry']['location']['lng']
    location = js['results'][0]['formatted_address']

    print('Latitude:', lat)
    print('Longitude:', lng)
    print('Location:', location)

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📊 Sample Output

Enter location: Ahmedabad
Retrieving: http://py4e-data.dr-chuck.net/json?address=Ahmedabad&key=42
Retrieved 1234 characters

Latitude: 23.0225
Longitude: 72.5714
Location: Ahmedabad, Gujarat, India

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🔑 Key Concepts Used

• urllib.request → Access web URLs
• urllib.parse.urlencode() → Encode parameters safely
• json.loads() → Convert JSON to Python dictionary
• SSL context → Ignore certificate errors during testing
• API communication using HTTP requests

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✅ Learning Outcome

After completing this program, you will understand:

• How APIs work
• How to fetch data from web services
• JSON parsing in Python
• Extracting nested data structures