Python Apis: Part 1

Author: R Zach Feeser

A classic approach to teaching code to screen interactions is by using a “turtle”. This approach asks students to use the coding language they are studying to move a basic “turtle” (it’s a dot) around on the X,Y axis of their screen. Python has a “Turtle Graphics Module” that is built on top of Tkinter, which is a more powerful, general purpose Python library for building GUIs (Graphical User Interfaces). Using this library, we will set the background as a world map of the planet Earth, replace the “turtle” with an International Space Station (ISS) icon, and then tell our new ISS-turtle to move according to real-time data provided by a RESTful API that tracks the actual location of the orbiting ISS.

Step 1 - Prerequisites to Perform this task.

  • Install latest version of python (python3.X)
  • Ubuntu 16.04 or greater.
  • Map to show International Space Station
  • Internatnional Space Station :)

Step 2 - Install python3 packages tkinter.

student@bchd:~$ sudo apt install python3--tk -y

Step 3 - Make a directory for your code.

student@bchd:~$ mkdir apicode

student@bchd:~$ cd apicode

student@bchd:~/apicode$

Step 4 - Create your python script and review!

You can do this with any of your favorite editors like vim, nano, or emacs. Here we just use leafpad.

student@bchd:~/apicode$ leafpad apicode.py

import urllib. request  # easily replaced by the requests library 
import json             # needed to translate JSON attachment because we use urllib.request

## Trace the ISS - earth-orbital space station
eoss = 'http://api.open-notify.org/iss-now.json'

## Call the webserv
trackiss = urllib.request.urlopen(eoss)

## put into file object
ztrack = trackiss.read()

## json 2 python data structure
result = json.loads(ztrack.decode('utf-8'))

## display our pythonic data
print("

Converted python data")
print (result)
input('
ISS data retrieved & converted. Press any key to continue')

location = result['iss_position']
lat = location['latitude']
lon = location['longitude']
print('
Latitude: ', lat)  

Step 5 - In your browser, check out the url, which is the value for the eoss variable.

Open your browser to a new tab with this URL: http://api.open-notify.org/iss-now.json

{"iss_position": {"latitude": "-27.8149", "longitude": "-112.1983"}, "timestamp": 1609361386, "message": "success"}

Step 7 - Run your python code!

student@bchd:~/apicode$ python3 apicode.py

Converted python data
{'iss_position1: {'longitude': '48.1352', 'latitude': '10.0497'}, 'timestamp': 1532355812, 'message': 'success’}

ISS data retrieved & converted. Press any key to continue

Latitude:  10.0.497
Longitude: 48.1352

Step 8 - Gather the rest of the Prerequisites.

student@bchd:~/apicode$ wget https://static.alta3.com/images/python/iss_map.gif -O iss_map.gif

student@bchd:~/apicode$ wget https://static.alta3.com/images/python/spriteiss.gif -O spriteiss.gif

Step 9 - Create an updated python script.

student@bchd:~/apicode$ leafpad apicode02.py

import turtle
import urllib.request
import json
## Trace |the ISS - earth-orbital space station
eoss = 'http://api.open-notify.org/iss-now.json'

## Call the webserv
trackiss = urllib.request.urlopen(eoss)

## put into file object
ztrack = trackiss.read()

## json 2 python data structure
result = json.loads(ztrack.decode('utf-8'))

## display our pythonic data
print("

Converted python data")
print(result)
input('
ISS data retrieved & converted. Press the ENTER key to continue')

location = result['iss_position']
lat = location['latitude']
lon = location['longitude']
print('
latitude: ', lat)
print('Longitude: ', lon)  

screen = turtle.Screen() # create a screen object
screen.setup(720, 360) # set the resolution

screen.setworldcoordinates(-180,-90,180,90)

screen.bgpic('iss map.gif')

screen.register shape('spriteiss.gif')

iss = turtle.Turtle()
iss.shape('spriteiss.gif')
iss.setheading(90)

lon = round(float(lon))
lat = round(float(lat))

iss.penup()
iss.goto(lon, lat)
turtle.mainloop()| # <-- this line should ALWAYS be at the bottom of your script. It prevents the graphic from closing!!

Step 10 - Run your new code!

student@bchd:~/apicode$ python3 apicode02.py

Converted python data
{'message': 'success', 'timestamp': 1532356659, 'iss_position': {'longitude': '93.1921', 'latitude': '46.5445'}}

ISS data retrieved & converted. Press the ENTER key to continue

Step 11 - Take a look at the Map that shows where the International Space Station is at the moment! Awesome!

api_python_turtle_iss.PNG api_python_turtle_iss.PNG

If you run that code again, you will see the International Space Station has moved coordinates. It moves with haste.

See PART 2 for more…

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