4.9.2 Lab – Integrate a REST API in a Python Application (Answers)

Feb 2, 2021 Last Updated: Feb 2, 2021 DEVASC v1 No Comments
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4.9.2 Lab – Integrate a REST API in a Python Application (Answers)

Objectives

  • Part 1: Launch the DEVASC VM
  • Part 2: Demonstrate the MapQuest Directions Application
  • Part 3: Get a MapQuest API Key
  • Part 4: Build the Basic MapQuest Direction Application
  • Part 5: Upgrade the MapQuest Directions Application with More Features
  • Part 6: Test Full Application Functionality

Background / Scenario

In this lab, you will create an application in Visual Studio Code (VS Code) that retrieves JSON data from the MapQuest Directions API, parses the data, and formats it for output to the user. You will use the GET Route request from the MapQuest Directions API. Review the GET Route Directions API documentation here:

https://developer.mapquest.com/documentation/directions-api/route/get/

Note: If the above link no longer works, search for “MapQuest API Documentation”.

Required Resources

  • 1 PC with operating system of your choice
  • Virtual Box or VMWare
  • DEVASC Virtual Machine

Instructions

Part 1: Launch the DEVASC VM

If you have not already completed the Lab – Install the Virtual Machine Lab Environment, do so now. If you have already completed that lab, launch the DEVASC VM now.

Part 2: Demonstrate the MapQuest Directions Application

Your instructor may demonstrate the MapQuest Directions Application and show you the script used to create it. However, you will create this script step by step in this lab.

The application asks for a starting location and a destination. It then requests JSON data from the MapQuest Directions API, parses it, and displays useful information.

>>>
Starting Location: Washington
Destination: Baltimore
URL: https://www.mapquestapi.com/directions/v2/route?key=your_api_key&from=Washington&to=Baltimore
API Status: 0 = A successful route call.

Directions from Washington to Baltimore
Trip Duration:   00:49:19
Kilometers:      61.32
Fuel Used (Ltr): 6.24
=============================================
Start out going north on 6th St/US-50 E/US-1 N toward Pennsylvania Ave/US-1 Alt N. (1.28 km)
Turn right onto New York Ave/US-50 E. Continue to follow US-50 E (Crossing into Maryland). (7.51 km)
Take the Balt-Wash Parkway exit on the left toward Baltimore. (0.88 km)
Merge onto MD-295 N. (50.38 km)
Turn right onto W Pratt St. (0.86 km)
Turn left onto S Calvert St/MD-2. (0.43 km)
Welcome to BALTIMORE, MD. (0.00 km)
=============================================

Starting Location: quit
>>>

Note: To see the JSON for the above output, you can copy the URL in a browser tab. However, you will need to replace your_api_key with the MapQuest API key you obtain in Part 3.

Instructor Note: The following is the answer script for the MapQuest Directions Application. You may want to show the script to the students and demonstrate its operation. However, we recommend that you do not give students the script. They will build it over the course of this lab.

#Replace "your_api_key" with your MapQuest API key

import urllib.parse
import requests

main_api = "https://www.mapquestapi.com/directions/v2/route?"
key = "your_api_key"


while True:
    orig = input("Starting Location: ")
    if orig == "quit" or orig == "q":
        break
    dest = input("Destination: ")
    if dest == "quit" or dest == "q":
        break
    url = main_api + urllib.parse.urlencode({"key":key, "from":orig, "to":dest}) 
    json_data = requests.get(url).json()
    print("URL: " + (url))
    json_data = requests.get(url).json()
    json_status = json_data["info"]["statuscode"]
    if json_status == 0:
        print("API Status: " + str(json_status) + " = A successful route call.\n")
        print("=============================================")
        print("Directions from " + (orig) + " to " + (dest))
        print("Trip Duration:   " + (json_data["route"]["formattedTime"]))
        print("Kilometers:      " + str("{:.2f}".format((json_data["route"]["distance"])*1.61)))
        print("Fuel Used (Ltr): " + str("{:.2f}".format((json_data["route"]["fuelUsed"])*3.78)))
        print("=============================================")
        for each in json_data["route"]["legs"][0]["maneuvers"]:
            print((each["narrative"]) + " (" + str("{:.2f}".format((each["distance"])*1.61) + " km)"))
        print("=============================================\n")
    elif json_status == 402:
        print("**********************************************")
        print("Status Code: " + str(json_status) + "; Invalid user inputs for one or both locations.")
        print("**********************************************\n")
    elif json_status == 611:
        print("**********************************************")
        print("Status Code: " + str(json_status) + "; Missing an entry for one or both locations.")
        print("**********************************************\n")
    else:
        print("************************************************************************")
        print("For Staus Code: " + str(json_status) + "; Refer to:")
        print("https://developer.mapquest.com/documentation/directions-api/status-codes")
        print("************************************************************************\n")

Part 3: Get a MapQuest API Key

Before building the application, you need to complete the following steps to get a MapQuest API key.

a. Go to: https://developer.mapquest.com/.

b. Click Sign Up at the top of the page.

c. Fill out the form to create a new account. For Company, enter Cisco Networking Academy Student.

d. After clicking Sign Me Up, you are redirected to the Manage Keys If you are redirected elsewhere, click Manage Keys from the list of options on the left.

e. Click Approve All Keys.

f. Expand My Application.

g. Copy your Consumer Key to a text file for future use. This will be the key you use for the rest of this lab.

Note: MapQuest may change the process for obtaining a key. If the steps above are no longer valid, search the internet for “steps to generate mapquest api key”.

Part 4: Build the Basic MapQuest Direction Application

In this Part, you will create a Python script to send a URL request to the MapQuest directions API. You will then test your API call. Throughout the rest of this lab, you will build your script in parts, saving the file with a new name each time. This will help with learning the pieces of the application as well as provide you a series of scripts that you can return to if you run into any problems in the current version of your application.

Step 1: Create a New File in VS Code.

You can use any tools you want to enter in Python commands and execute the Python code. However, this lab will demonstrate building the application in VS Code.

a. Open VS Code. There is a shortcut on the Desktop, for your convenience.

b. Select File > Open Folder…

c. Navigate to the ~/labs/devnet-src/mapquest directory and click OK. This directory is currently empty and is where you will store each iteration of your application.

d. Select File > New File.

e. Select File > Save as… and name the file mapquest_parse-json_1.py and click Save.

Step 2: Importing modules for the application.

To begin your script for parsing JSON data, you will need to import two modules from the Python library: requests and urllib.parse. The requests module provides functions for retrieving JSON data from a URL. The urllib.parse module provides a variety of functions that will enable you to parse and manipulate the JSON data you receive from a request to a URL.

a. Add the following import statements at the top of your script.

import urllib.parse
import requests

b. Select Terminal > New Terminal to open a Terminal inside VS Code.

Save and run your script. You should get no errors. You should save and run your scripts often to test code functionality.

devasc@labvm:~/labs/devnet-src/mapquest$ python3 mapquest_parse-json_1.py 
devasc@labvm:~/labs/devnet-src/mapquest$
Step 3: Build the URL for the request to the MapQuest directions API.

The first step in creating your API request is to construct the URL that your application will use to make the call. Initially, the URL will be the combination of the following variables:

  • main_api – the main URL that you are accessing
  • orig – the parameter to specify your point of origin
  • dest – the parameter to specify your destination
  • key – the MapQuest API key you retrieved from the developer website

a. Create variables to build the URL that will be sent in the request. In the following code, replace your_api_key with the Consumer Key you copied from your MapQuest developer account.

main_api = "https://www.mapquestapi.com/directions/v2/route?"
orig = "Washington, D.C."
dest = "Baltimore, Md"
key = "your_api_key"

b. Combine the four variables main_api, orig, dest, and key to format the requested URL. Use the urlencode method to properly format the address value. This function builds the parameters part of the URL and converts possible special characters in the address value into acceptable characters (e.g. space into “+” and a comma into “%2C”).

url = main_api + urllib.parse.urlencode({"key":key, "from":orig, "to":dest})

c. Create a variable to hold the reply of the requested URL and print the returned JSON data. The json_data variable holds a Python’s Dictionary representation of the json reply of the get method of the requests The requests.get will make the API call to the MapQuest API. The print statement will be used temporarily to check the returned data. You will replace this print statement with more sophisticated display options later in the lab.

json_data = requests.get(url).json()
print(json_data)

d. Your final code should look like this, but with a different value for the key.

import urllib.parse
import requests

main_api = "https://www.mapquestapi.com/directions/v2/route?"
orig = "Washington, D.C."
dest = "Baltimore, Md"
key = "fZadaFOY22VIEEemZcBFfxl5vjSXIPpZ" #Replace with your MapQuest key

url = main_api + urllib.parse.urlencode({"key":key, "from":orig, "to":dest})

json_data = requests.get(url).json()
print(json_data)
Step 4: Test the URL request.

a. Save and run your mapquest_parse-json_1.py script and verify it works.

b. Troubleshoot your code, if necessary. Although your output might be slightly different, you should get a JSON response similar to the following. Notice that the output is a dictionary with two key/value pairs. The value for the key route is another dictionary that includes additional dictionaries and lists. The key info includes the statuscode key/value pair that you will use later in the lab.

devasc@labvm:~/labs/devnet-src/mapquest$ python3 mapquest_parse-json_1.py
{'route': {'hasTollRoad': False, 'hasBridge': True, 'boundingBox': {'lr': {'lng': -76.612137, 'lat': 38.892063}, 'ul': {'lng': -77.019913, 'lat': 39.290443}}, 'distance': 38.089, 'hasTimedRestriction': False, 'hasTunnel': False, 'hasHighway': True, 'computedWaypoints': [], 'routeError': {'errorCode': -400, 'message': ''}, 'formattedTime': '00:49:29', 'sessionId': '5eadfc17-00ee-5f21-02b4-1a24-0647e6e69816', 'hasAccessRestriction': False, 'realTime': 2915, 'hasSeasonalClosure': False, 'hasCountryCross': False, 'fuelUsed': 1.65, 'legs': [{'hasTollRoad': False, 'hasBridge': True, 'destNarrative': 'Proceed to BALTIMORE, MD.', 'distance': 38.089, 'hasTimedRestriction': False, 'hasTunnel': False, 'hasHighway': True, 'index': 0, 'formattedTime': '00:49:29', 'origIndex': -1, 'hasAccessRestriction': False, 'hasSeasonalClosure': False, 'hasCountryCross': False, 'roadGradeStrategy': [[]], 'destIndex': 3, 'time': 2969, 'hasUnpaved': False, 'origNarrative': '', 'maneuvers': [{'distance': 0.792, 'streets': ['6th St', 'US-50 E', 'US-1 N'], 'narrative': 'Start out going north on 6th St/US-50 E/US-1 N toward Pennsylvania Ave/US-1 Alt N.', 'turnType': 0, 'startPoint': {'lng': -77.019913, 'lat': 38.892063}, 'index': 0, 'formattedTime': '00:02:06', 'directionName': 'North', 'maneuverNotes': [], 'linkIds': [], 'signs': [{'extraText': '', 'text': '50', 'type': 2, 'url': 'http://icons.mqcdn.com/icons/rs2.png?n=50&d=EAST', 'direction': 8}, {'extraText': '', 'text': '1', 'type': 2, 'url': 'http://icons.mqcdn.com/icons/rs2.png?n=1&d=NORTH', 
<<<<<                >>>>>
      output omitted
<<<<<                >>>>>
'geocodeQuality': 'CITY', 'adminArea1Type': 'Country', 'adminArea3Type': 'State', 'latLng': {'lng': -76.61233, 'lat': 39.29044}}], 'time': 2969, 'hasUnpaved': False, 'locationSequence': [0, 1], 'hasFerry': False}, 'info': {'statuscode': 0, 'copyright': {'imageAltText': '© 2019 MapQuest, Inc.', 'imageUrl': 'http://api.mqcdn.com/res/mqlogo.gif', 'text': '© 2019 MapQuest, Inc.'}, 'messages': []}}
devasc@labvm:~/labs/devnet-src/mapquest$

c. Change the orig and dest variables. Rerun the script to get different results. To ensure the results you want, it is best to include both the city and the state for cities in the USA. When referring to cities in other countries, you can usually use either the English name for the city and country or the native name. For example:

orig = "Rome, Italy"
dest = "Frascati, Italy"

or

orig = "Roma, Italia"
dest = "Frascati, Italia"
Step 5: Print the URL and check the status of the JSON request.

Now that you know the JSON request is working, you can add some more functionality to the application.

a. Save your script as mapquest_parse-json_2.py.

b. Delete the print(json_data) statement as you no longer need to test that the request is properly formatted.

c. Add the statements below, which will do the following:

  • Print the constructed URL so that the user can see the exact request made by the application.
  • Parse the JSON data to obtain the statuscode
  • Start an if loop that checks for a successful call, which is indicated by a returned value of 0. Add a print statement to display the statuscode value and its meaning. The \n adds a blank line below the output.

Later in this lab, you will add elif and else statements for different statuscode values.

print("URL: " + (url))

json_data = requests.get(url).json()
json_status = json_data["info"]["statuscode"]

if json_status == 0:
    print("API Status: " + str(json_status) + " = A successful route call.\n")
Step 6: Test status and URL print commands.

a. The example here uses the following parameters.

orig = "Washington, D.C."
dest = "Baltimore, Md"

b. Save and run your mapquest_parse-json_2.py script and verify it works. Troubleshoot your code, if necessary. You should get output similar to the following. Notice your key is embedded in the URL request.

devasc@labvm:~/labs/devnet-src/mapquest$ python3 mapquest_parse-json_2.py
URL: https://www.mapquestapi.com/directions/v2/route?key=fZadaFOY22VIEEemZcBFfxl5vjSXIPpZ&from=Washington%2C+D.C.&to=Baltimore%2C+Md
API Status: 0 = A successful route call.

devasc@labvm:~/labs/devnet-src/mapquest$
Step 7: Add User input for starting location and destination.

You have used static values for the location variables. However, the application requires that the user input these. Complete the following steps to update your application:

a. Save your script as mapquest_parse-json_3.py.

b. Delete the current orig and dest

c. Rewrite the orig and dest to be within a while loop in which it requests user input for the starting location and destination. The while loop allows the user to continue to make requests for different directions. Add the following code, highlighted below, after the key parameter. Be sure all the remaining code is correctly indented within the while loop.

import urllib.parse
import requests

main_api = "https://www.mapquestapi.com/directions/v2/route?" 
key = "fZadaFOY22VIEEemZcBFfxl5vjSXIPpZ"

while True:
   orig = input("Starting Location: ")
   dest = input("Destination: ")
   url = main_api + urllib.parse.urlencode({"key": key, "from":orig, "to":dest})
   print("URL: " + (url))
   json_data = requests.get(url).json()
   json_status = json_data["info"]["statuscode"]
   if json_status == 0:
       print("API Status: " + str(json_status) + " = A successful route call.\n")
Step 8: Test user input functionality.

Run your mapquest_parse-json_3.py script and verify it works. Troubleshoot your code, if necessary. You should get output similar to what is shown below. To end the program, enter Ctrl+C. You will get a KeyboardInterrupt error as shown in the output below. To stop the application more gracefully, you will add quit functionality in the next step.

devasc@labvm:~/labs/devnet-src/mapquest$ python3 mapquest_parse-json_3.py
Starting Location: Washington, D.C.
Destination: Baltimore, Md
URL: https://www.mapquestapi.com/directions/v2/route?key=fZadaFOY22VIEEemZcBFfxl5vjSXIPpZ&from=Washington%2C+D.C.&to=Baltimore%2C+Md
API Status: 0 = A successful route call.

Starting Location: ^CTraceback (most recent call last):
  File "mapquest_parse-json_3.py", line 9, in 
    orig = input("Starting Location: ")
KeyboardInterrupt

devasc@labvm:~/labs/devnet-src/mapquest$
Step 9: Add quit functionality to the application.

Instead of forcing the application to quit with a keyboard interrupt, you will add the ability for the user to enter q or quit as keywords to quit the application. Complete the following steps to update your application:

a. Save your script as mapquest_parse-json_4.py.

b. Add an if statement after each location variable to check if the user enters q or quit, as shown below.

while True:
    orig = input("Starting Location: ")
    if orig == "quit" or orig == "q":
        break
    dest = input("Destination: ")
    if dest == "quit" or dest == "q":
        break
Step 10: Test the quit functionality.

Run your mapquest_parse-json_4.py script four times to test each location variable. Verify that both quit and q will end the application. Troubleshoot your code, if necessary. You should get output similar to the following.

devasc@labvm:~/labs/devnet-src/mapquest$ python3 mapquest_parse-json_4.py
Starting Location: q
devasc@labvm:~/labs/devnet-src/mapquest$ python3 mapquest_parse-json_4.py
Starting Location: quit
devasc@labvm:~/labs/devnet-src/mapquest$ python3 mapquest_parse-json_4.py
Starting Location: Washington, D.C
Destination: q
devasc@labvm:~/labs/devnet-src/mapquest$ python3 mapquest_parse-json_4.py
Starting Location: Washington, D.C.
Destination: quit
devasc@labvm:~/labs/devnet-src/mapquest$
Step 11: Display the JSON data in JSONView.

The Chromium browser in the DEVASC VM includes the JSONView extension. You can use this to view a JSON object in a readable, colored, and collapsible format.

a. Run your mapquest_parse-json_4.py again and copy the code returned for the URL. Do not use the code below. Your result will include your API key.

devasc@labvm:~/labs/devnet-src/mapquest$ python3 mapquest_parse-json_4.py
Starting Location: Washington, D.C.
Destination: Baltimore, Md
URL: https://www.mapquestapi.com/directions/v2/route?key=fZadaFOY22VIEEemZcBFfxl5vjSXIPpZ&from=Washington%2C+D.C.&to=Baltimore%2C+Md
API Status: 0 = A successful route call.

Starting Location: quit
devasc@labvm:~/labs/devnet-src/mapquest$

b. Paste the URL in the Chromium browser address field.

c. Collapse the JSONView data by selecting the dash “-” before route, you will see that there are two root dictionaries: route and info.

{
 - route:{
      hasTollRoad: false,
      hasBridge: true,
 <output omitted>

You will see that there are two root dictionaries: route and info. Notice that info has the statuscode key/value paired used in your code.

{
 + route: {},
 - info: {
       statuscode: 0,
     - copyright: {
           imageAltText: "© 2019 MapQuest, Inc.",
           imageUrl: "http://api.mqcdn.com/res/mqlogo.gif",
           text: "© 2019 MapQuest, Inc."
       },
       messages: [ ]
   }
}

d. Expand the route dictionary (click on the plus sign “+” before route) and investigate the rich data. There are values to indicate whether the route has toll roads, bridges, tunnels, highways, closures, or crosses into other countries. You should also see values for distance, the total time the trip will take, and fuel usage. To parse and display this data in your application, you would specify the route dictionary and then select key/value pair you want to print. You will do some parsing of the route dictionary in the next part of the lab.

Part 5: Upgrade the MapQuest Directions Application with More Features

In this Part, you will add additional features to your MapQuest Directions Application to provide more information to the user. You will include some trip summary information and then a list of the directions parsed from the legs dictionary. As a final step, you will add some basic error checking to validate user input.

Step 1: Display trip summary information to include duration, distance, and fuel used.

a. Save your script as mapquest_parse-json_5.py.

b. Below the API status print command, add several print statements that display the from and to locations, as well as the formattedTime, distance, and fuelUsed

The additional statements also include print statements that will display a double line before the next request for a starting location. Make sure these statements are embedded in the while True function.

if json_status == 0:
        print("API Status: " + str(json_status) + " = A successful route call.\n")
        print("=============================================")
        print("Directions from " + (orig) + " to " + (dest))
        print("Trip Duration:   " + (json_data["route"]["formattedTime"]))
        print("Miles:           " + str(json_data["route"]["distance"]))
        print("Fuel Used (Gal): " + str(json_data["route"]["fuelUsed"]))
        print("=============================================")

c. Save and run mapquest_parse-json_5.py to see the following output.

devasc@labvm:~/labs/devnet-src/mapquest$ python3 mapquest_parse-json_5.py 
Starting Location: Washington, D.C.
Destination: Baltimore, Md
URL: https://www.mapquestapi.com/directions/v2/route?key=fZadaFOY22VIEEemZcBFfxl5vjSXIPpZ&from=Washington%2C+D.C.&to=Baltimore%2C+Md
API Status: 0 = A successful route call.

=============================================
Directions from Washington, D.C. to Baltimore, Md
Trip Duration: 00:49:29
Miles: 38.089
Fuel Used (Gal): 1.65
=============================================
Starting Location: q
devasc@labvm:~/labs/devnet-src/mapquest$

d. By defauilt, MapQuest uses the imperial system and there is not a request parameter to change data to the metric system. Therefore, you should probably convert your application to display metric values, as shown below.

print("Kilometers:      " + str((json_data["route"]["distance"])*1.61))
print("Fuel Used (Ltr): " + str((json_data["route"]["fuelUsed"])*3.78))

e. Run the modified mapquest_parse-json_5.py script to see the following output:

devasc@labvm:~/labs/devnet-src/mapquest$ python3 mapquest_parse-json_5.py
Starting Location: Washington, D.C.
Destination: Baltimore, Md
URL: https://www.mapquestapi.com/directions/v2/route?key=fZadaFOY22VIEEemZcBFfxl5vjSXIPpZ&from=Washington%2C+D.C.&to=Baltimore%2C+Md
API Status: 0 = A successful route call.

=============================================
Directions from Washington, D.C. to Baltimore, Md
Trip Duration: 00:49:29
Kilometers: 61.32329
Fuel Used (Ltr): 6.236999999999999
=============================================
Starting Location: q
devasc@labvm:~/labs/devnet-src/mapquest$

f. The extra decimal places for Kilometers and Fuel Used are not helpful. Use the “{:.2f}”.format argument to format the float values to 2 decimal places before converting them to string values, as shown below. Each statement should be on one line.

print("Kilometers:      " + str("{:.2f}".format((json_data["route"]["distance"])*1.61)))
print("Fuel Used (Ltr): " + str("{:.2f}".format((json_data["route"]["fuelUsed"])*3.78)))
Step 2: Test the parsing and formatting functionality.

Save and run your mapquest_parse-json_5.py script to verify it works. Troubleshoot your code, if necessary. Make sure you have all the proper opening and closing parentheses. You should get output similar to the following.

devasc@labvm:~/labs/devnet-src/mapquest$ python3 mapquest_parse-json_5.py
Starting Location: Washington, D.C.
Destination: Baltimore, Md
URL: https://www.mapquestapi.com/directions/v2/route?key=fZadaFOY22VIEEemZcBFfxl5vjSXIPpZ&from=Washington%2C+D.C.&to=Baltimore%2C+Md
API Status: 0 = A successful route call.

=============================================
Directions from Washington, D.C. to Baltimore, Md
Trip Duration: 00:49:29
Kilometers: 61.32
Fuel Used (Ltr): 6.24
=============================================
Starting Location: q
devasc@labvm:~/labs/devnet-src/mapquest$
Step 3: Inspect the maneuvers list in the JSON data.

a. Now you are ready to display the step-by-step directions from the starting location to the destination. Return to the Chromium browser where earlier you viewed the output in JSONView. If you closed the browser, copy the URL from last time you ran the program and paste it into the browser address bar.

b. Inside the route dictionary, locate the legs The legs list includes one big dictionary with most of the JSON data. Find the maneuvers list and collapse each of the seven dictionaries inside, as shown below (click the “–” minus sign to toggle it to a “+” plus sign). If you are using different locations, you will probably have a different number of maneuver dictionaries.

- legs: [
    - {
         hasTollRoad: false,
         hasBridge: true,
         destNarrative: "Proceed to BALTIMORE, MD.",
         distance: 38.089,
         hasTimedRestriction: false,
         hasTunnel: false,
         hasHighway: true,
         index: 0,
         formattedTime: "00:49:29",
         origIndex: -1,
         hasAccessRestriction: false,
         hasSeasonalClosure: false,
         hasCountryCross: false,
       - roadGradeStrategy: [
             [ ]
         ],
         destIndex: 3,
         time: 2969,
               hasUnpaved: false,
         origNarrative: "",
      - maneuvers: [
          + {…},
          + {…},
          + {…},
          + {…},
          + {…},
          + {…},
          + {…}
         ],
         hasFerry: false
     }
        ],
      - options: {

c. Expand the first dictionary in the maneuvers Each dictionary contains a narrative key with a value, such as “Start out going north…”, as shown below. You need to parse the JSON data to extract the value for the narrative key to display inside your application.

- legs: [
    - {
       hasTollRoad: false,
       hasBridge: true,
       destNarrative: "Proceed to BALTIMORE, MD.",
       distance: 38.089,
       hasTimedRestriction: false,
       hasTunnel: false,
       hasHighway: true,
       index: 0,
       formattedTime: "00:49:29",
       origIndex: -1,
       hasAccessRestriction: false,
       hasSeasonalClosure: false,
       hasCountryCross: false,
     - roadGradeStrategy: [
           [ ]
       ],
       destIndex: 3,
       time: 2969,
             hasUnpaved: false,
       origNarrative: "",
    - maneuvers: [
        - {
             distance: 0.792,
           - streets: [
                 "6th St",
                 "US-50 E",
                 "US-1 N"
             ],
             narrative: "Start out going north on 6th St/US-50E/US-1 N toward Pennsylvania Ave/US-1 Alt N.",
             turnType: 0,
           - startPoint: {
                lng: -77.019913,
                lat: 38.892063
             },
             index: 0,
             formattedTime: "00:02:06",
             directionName: "North",
             maneuverNotes: [ ],
             linkIds: [ ],
           - signs: [
               - {
                     extraText: "",
                     ext: "50",
                     type: 2,
<output omitted>

Note: Word wrap was added for the value in the narrative for display purposes.

Step 4: Add a for loop to iterate through the maneuvers JSON data.

Complete the following steps to upgrade the application to display the value for the narrative key. You will do this by creating a for loop to iterate through the maneuvers list, displaying the narrative value for each maneuver from starting location to destination.

a. Save your script as mapquest_parse-json_6.py.

b. Add a for loop, highlighted below, after the second double line print statement. The for loop iterates through each maneuvers list and does the following:

  1. Prints the narrative
  2. Converts miles to kilometers with *1.61.
  3. Formats the kilometer value to print only two decimal places with the “{:.2f}”.format

c. Add a print statement that will display a double line before the application asks for another starting location, as shown below.

Note: The double line print statement is not indented within the for loop. It therefore is part of the previous if statement that checks the statuscode parameter.

print("Fuel Used (Ltr): " + str("{:.2f}".format((json_data["route"]["fuelUsed"])*3.78)))
print("=============================================")
for each in json_data["route"]["legs"][0]["maneuvers"]:
print((each["narrative"]) + " (" + str("{:.2f}".format((each["distance"])*1.61) + " km)"))
print("=============================================\n")
Step 5: Activity – Test the JSON iteration.

Save and run your mapquest_parse-json_6.py script to verify it works. Troubleshoot your code, if necessary. You should get an output similar to the following:

devasc@labvm:~/labs/devnet-src/mapquest$ python3 mapquest_parse-json_6.py 
Starting Location: Washington, D.C.
Destination: Baltimore, Md
URL: https://www.mapquestapi.com/directions/v2/route?key=fZadaFOY22VIEEemZcBFfxl5vjSXIPpZ&from=Washington%2C+D.C.&to=Baltimore%2C+Md
API Status: 0 = A successful route call.

=============================================
Directions from Washington, D.C. to Baltimore, Md
Trip Duration: 00:49:29
Kilometers: 61.32
Fuel Used (Ltr): 6.24
=============================================
Start out going north on 6th St/US-50 E/US-1 N toward Pennsylvania Ave/US-1 Alt N. (1.28 km)
Turn right onto New York Ave/US-50 E. Continue to follow US-50 E (Crossing into Maryland). (7.51 km)
Take the Balt-Wash Parkway exit on the left toward Baltimore. (0.88 km)
Merge onto MD-295 N. (50.38 km)
Turn right onto W Pratt St. (0.86 km)
Turn left onto S Calvert St/MD-2. (0.43 km)
Welcome to BALTIMORE, MD. (0.00 km)
=============================================

Starting Location: q
devasc@labvm:~/labs/devnet-src/mapquest$
Step 6: Check for invalid user input.

Now you are ready to add one final feature to your application to report an error when the user enters invalid data. Recall that you started an if loop to make sure the returned statuscode equals 0 before parsing the JSON data:

json_status = json_data["info"]["statuscode"]

    if json_status == 0:
        print("API Status: " + str(json_status) + " = A successful route call.\n")

But what happens if the statuscode is not equal to 0? For example, the user might enter an invalid location or might not enter one or more locations. If so, then the application displays the URL and asks for a new starting location. The user has no idea what happened.

a. To cause your application to fail without user notification, try the following values in your application. You should see similar results.

devasc@labvm:~/labs/devnet-src/mapquest$ python3 mapquest_parse-json_6.py 
Starting Location: Washington, D.C.
Destination: Beijing, China
URL: https://www.mapquestapi.com/directions/v2/route?key=fZadaFOY22VIEEemZcBFfxl5vjSXIPpZ&from=Washington%2C+D.C.&to=Beijing%2C+China
Starting Location: Washington, D.C.
Destination: Bal
URL: https://www.mapquestapi.com/directions/v2/route?key=fZadaFOY22VIEEemZcBFfxl5vjSXIPpZ&from=Washington%2C+D.C.&to=Bal
Starting Location: q
devasc@labvm:~/labs/devnet-src/mapquest$

b. Copy one of the URLs to a Chromium browser tab. Notice that the only entry in route dictionary is a routeError dictionary with the errorCode In the info dictionary, the statuscode is 402. Therefore, your if loop never executed the code for when the statuscode is 0.

c. Save your script as mapquest_parse-json_7.py.

d. To provide error information when statuscode is equal to 402, 611, or another value, add two elif statements and an else statement to your if loop. Your elif and else statements must align with the previous if After the last double line print statement under the if json_status == 0, add the following elif and else statements:

if json_status == 0:
       <statements omitted>
       for each in json_data["route"]["legs"][0]["maneuvers"]:
           print((each["narrative"]) + " (" + str("{:.2f}".format((each["distance"])*1.61) + " km)"))
        print("=============================================\n")
    elif json_status == 402:
        print("**********************************************")
        print("Status Code: " + str(json_status) + "; Invalid user inputs for one or both locations.")
        print("**********************************************\n")
    elif json_status == 611:
        print("**********************************************")
        print("Status Code: " + str(json_status) + "; Missing an entry for one or both locations.")
        print("**********************************************\n")
    else:
        print("************************************************************************")
        print("For Staus Code: " + str(json_status) + "; Refer to:")
        print("https://developer.mapquest.com/documentation/directions-api/status-codes")
        print("************************************************************************\n")

The first elif statement prints if the statuscode value is 402 for an invalid location. The second elif statement prints if the statuscode value is 611 because the user did not provide an entry for one or both locations. The else statement prints for all other statuscode values, such as when the MapQuest site returns an error. The else statement ends the if/else loop and returns the application to the while loop.

Part 6: Test Full Application Functionality

Run your mapquest_parse-json_7.py script and verify it works. Troubleshoot your code, if necessary. Test all the features of the application. You should get output similar to the following.

devasc@labvm:~/labs/devnet-src/mapquest$ python3 mapquest_parse-json_7.py 
Starting Location: Washington, D.C.
Destination: Baltimore, Md
URL: https://www.mapquestapi.com/directions/v2/route?key=fZadaFOY22VIEEemZcBFfxl5vjSXIPpZ&from=Washington%2C+D.C.&to=Baltimore%2C+Md
API Status: 0 = A successful route call.

=============================================
Directions from Washington, D.C. to Baltimore, Md
Trip Duration: 00:49:29
Kilometers: 61.32
Fuel Used (Ltr): 6.24
=============================================
Start out going north on 6th St/US-50 E/US-1 N toward Pennsylvania Ave/US-1 Alt N. (1.28 km)
Turn right onto New York Ave/US-50 E. Continue to follow US-50 E (Crossing into Maryland). (7.51 km)
Take the Balt-Wash Parkway exit on the left toward Baltimore. (0.88 km)
Merge onto MD-295 N. (50.38 km)
Turn right onto W Pratt St. (0.86 km)
Turn left onto S Calvert St/MD-2. (0.43 km)
Welcome to BALTIMORE, MD. (0.00 km)
=============================================

Starting Location: Moscow, Russia
Destination: Beijing, China
URL: https://www.mapquestapi.com/directions/v2/route?key=fZadaFOY22VIEEemZcBFfxl5vjSXIPpZ&from=Moscow%2C+Russia&to=Beijing%2C+China
API Status: 0 = A successful route call.

=============================================
Directions from Moscow, Russia to Beijing, China
Trip Duration: 84:31:10
Kilometers: 7826.83
Fuel Used (Ltr): 793.20
=============================================
Start out going west on Кремлёвская набережная/Kremlin Embankment. (0.37 km)
Turn slight right onto ramp. (0.15 km)
Turn slight right onto Боровицкая площадь. (0.23 km)
<output omitted>
Turn slight left onto 前门东大街/Qianmen East Street. (0.31 km)
Turn left onto 广场东侧路/E. Guangchang Rd. (0.82 km)
广场东侧路/E. Guangchang Rd becomes 东长安街/E. Chang'an Str. (0.19 km)
Welcome to BEIJING. (0.00 km)
=============================================

Starting Location: Washington, D.C.
Destination: Beijing, China
URL: https://www.mapquestapi.com/directions/v2/route?key=fZadaFOY22VIEEemZcBFfxl5vjSXIPpZ&from=Washington%2C+D.C.&to=Beijing%2C+China
**********************************************
Status Code: 402; Invalid user inputs for one or both locations.
**********************************************

Starting Location: Washington, D.C.
Destination: Bal
URL: https://www.mapquestapi.com/directions/v2/route?key=fZadaFOY22VIEEemZcBFfxl5vjSXIPpZ&from=Washington%2C+D.C.&to=Bal
**********************************************
Status Code: 402; Invalid user inputs for one or both locations.
**********************************************

Starting Location: Washington, D.C.
Destination: 
URL: https://www.mapquestapi.com/directions/v2/route?key=ANUqwkHlgDv1vlsyBPtVrFeX8uu6agjA&from=Washington%2C+D.C.&to=
**********************************************
Status Code: 611; Missing an entry for one or both locations.
**********************************************

Starting Location: quit
devasc@labvm:~/labs/devnet-src/mapquest$

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