Python3. Filling the Tank

Ground-up

In previous post I tried to show you how to write simple program in neovim and run using python3. Today I want to fill in the gaps in your knowledge of my understanding of how developer work. First of all we will touch on some Vim commands that migh be useful and then we'll build a tool that show where International Space Station is and who is currently in space. Maybe we will call an Uber for them later, right now they have to use their scooters.

Let's start with

shell:


nvim round_globe.py

Nvim

Then please feel free to skip to the next section if you already feel comfortable with nvim. I want to elaborate a little bit on the subject.

So you probably want to know how to copy & paste? My solution:

viml:


<v>
" use arrow keys or h,j,k,l to highlight and...
<y>
" place cursor in the place where you want to paste and...
<P>

Do you want to reorganize your codebase and move lines around?

viml:


<V>
" highlight
<x>
" cursor in the place and...
<p>

To undo last step, use <u> and <C-r> to redo.

You can open more than one file, in separate window or tab. I show you the tab option here.

viml:


:tabedit i_swear_i_rockyou.py
" switch to previous tab
:tabprevious
" then to close a tab and all it's windows (you know you can
" use <tab> key to autocomplete?)
:tabclose

I hope it helps.

Helpful Vim links

Once more, I encourage you to explore on theese cheatsheets and experiment in your terminal window, tab or webshell.

If you use some flavour of Nutek, you can simply try this out in your terminal.

shell:


w3m https://devhints.io/vim

w3m https://vim.rtorr.com/

I will teach you more about w3m later on, but to quit it - simply <q><y>

Enough is enough

If you can't stand the pace, or my attitude, or simply want to explore... Here's an email from freecCodeCamp where the subject is JavaScript.

plaintext:


Quincy Larson <quincy@freecodecamp.org>
6:11 AM (9 hours ago)
to me

Here are this week's five links that are worth your time:

1. Learn React for Beginners. This new freeCodeCamp Front-End JavaScript course will teach you all about React Hooks, State, the Context API, and more. You'll code along with three experienced software engineers, building projects step-by-step. (8 hour YouTube course): https://www.freecodecamp.org/news/learn-react-from-three-all-star-instructors/

2. And if you'd prefer to learn Angular, I'm thrilled to share this course with you as well: Learn Angular and TypeScript for Beginners. This in-depth course will teach you TypeScript Data Types, Angular Directives, Components, RxJS, and Lifecycle Hooks. (18 hour YouTube course): https://www.freecodecamp.org/news/angular-for-beginners-course/

(...)

Python class

It's not that you're my student. It's just object oriented programming concept. Most, if not all, python types are object and you can create your own types, classes, too. Create your environment and I show you how to call from Houston to space.

shell:


 case you forgot how to prepare your environment, here's how
python3 -m venv space_station
source space_station/bin/activate
 you see now?
(space_station)% python -m pip install requests
 the (space_station)% part, as it is only for reference

Import

It's time for the show to begin. Clear out your round_globe.py file (you might need to put it in the same directory as your environment). Starting simple, import statements. We will use json and requests libraries. Put them in separate lines.

python:


 statemnts. What we will use.
import requests
import json

ISS

Now we go big. Whole class. ISS - International Space Station. It is initialized without any arguments, then proceeds with a get request to an external api resource. APIs are services on the Internet that perform actions and/or sends data. You can even create your own and host for other well behaved users! I check for a HTTP status code 200 - that means everything is OK and I parse the response json data to self.lat and self.lon class instance variables. If there is an error, we print out the status code and exit.

Then I make two methods get_lat and get_lon which return the stored latitude and longitude ISS position variables. You can see here that accessing instance variables, as well as functions must be prepended with self., but you are not limited to creating only such objects. In __init__ we can observe use of local variable response and status_code which dies out when out of scope and you can no longer access them from other parts of code.

The last bit of information is __str__(self) method that when used to print object, will returned stated action replacing {} with subsequent values.

The last thing I want to say is about indentation, namely tabs, or spaces, which must match the hierarchical pattern and be consistent. Otherwise you might spend much more time debugging your application than you should.

python:


 class definition
class ISS():
    # Class to represent the International Space Station
    # initialize the class
    def __init__(self):
        # get the ISS location data
        response = requests.get("http://api.open-notify.org/iss-now.json")
        status_code = response.status_code
        # if the response was successful, parse the JSON data
        if status_code == 200:
            response_json = response.json()
            self.lat = response_json['iss_position']['latitude']
            self.lon = response_json['iss_position']['longitude']
        # if the response was not successful, print the status code and exit
        else:
            print("Error: " + str(status_code))
            exit(1)

    # return self.lat, self.lon
    def get_lat(self):
        return self.lat
    def get_lon(self):
        return self.lon

    # pretty print the ISS location
    def __str__(self):
        return "ISS location: latitude: {}, longitude: {}" \
                .format(self.get_lat(), self.get_lon())

Where we at now

To make the round_globe program much more exciting I introduce another class that retrieves the Earth position of provided at initialization attributes latitude and longitude. The concept stays the same.

python:


 class definition
class PositionRelativeToEarth():
    # Initialize the class
    def __init__(self, latitude, longitude):
        # get the position data
        response = requests.get(
                "https://api.bigdatacloud.net/data/reverse-geocode-client?latitude={}&longitude={}" \
                        .format(latitude, longitude))
        status_code = response.status_code
        # if the response was successful, parse the JSON data
        if status_code == 200:
            response_json = response.json()
            self.country = response_json['countryName']
            self.countryCode = response_json['countryCode']
            self.city = response_json['locality']
        # if the response was not successful, print the status code and exit
        else:
            print("Error: " + str(status_code))
            exit(1)

    # pretty print position
    def __str__(self):
        return "Position: country: {}, countryCode: {}, city: {}" \
                .format(self.country, self.countryCode, self.city)

Astronauts

I want to show you, that you are not limited to sequential program structure, and you can store methods outside of classes too. This one gets our heroes, astronauts in space and when the method is invoked will print out this data to console.

python:


.get("http://api.open-notify.org/astros.json")
 is in space?
def astros():
    # make the request
    response = requests.get("http://api.open-notify.org/astros.json")
    status_code = response.status_code
    # if the response was successful, parse the JSON data
    if status_code == 200:
        data = response.json()
        # Get number of people in space.
        number = data["number"]
        print("Number of people in space: {}".format(number))
        people = data["people"]
        # Print people in space.
        print("People in space: ")
        for person in people:
            print(person["name"])
    # if the response was not successful, print the status code and exit
    else:
        print("Error: " + str(status_code))
        exit(1)

Aggregate classes and methods

In this part of code I group all the bits provided before to contitute a program that will run. I have to call the astros() function, initialize ISS class and using another way of representing text data f"{1+1}" clause I pretty print the Internationa Space Station position relative to our globe, and at last I initilize PositionRelativeToEarth with __init__ attributes using iss variable.

python:


 function
def main():
    astros()
    iss = ISS()
    print(f"{iss}")
    position = PositionRelativeToEarth(iss.lat, iss.lon)
    print(position)

Run the script

The last part of code tells the Python interpreter to call main function when file is run with python or python3.

python:


 main function only if this file is executed
if __name__ == '__main__':
    main()

That would be it for Today. Lookup where the International Space Station is now and who is in the space when you please. You have me now finished.

Cleanup

Deactivate

Deactivate command, will free you from Python's virtual environment

shell:


deactivate

2022-09-09 14:28:32 +0200 by Neosb

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Python3. Filling the Tank

Table of contents:

Ground-up

Nvim

Helpful Vim links

Enough is enough

Python class

Import

ISS

Where we at now

Astronauts

Aggregate classes and methods

Run the script

Cleanup

Deactivate

2022-09-09 14:28:32 +0200 by Neosb

Comments: