Do you want to learn Solidity and create your own dApps and smart contracts? This free online course gives you a comprehensive overview that is aimed to be more accessible than the Solidity documentation but still complete and descriptive.

Multimodal Learning: Each tutorial comes with a tutorial video that helps you grasp the concepts in a more interactive manner.

Are you ready to build your skills as a highly sought-after Blockchain Developer or Solidity Engineer? Let’s dive right in!

Basic Introduction and Overview

1. Introduction to Smart Contracts and Solidity
2. How to Create Your Own Token in Solidity – Easy Example
3. Blockchain Basics of Smart Contracts and Solidity
4. Mastering the Ethereum Virtual Machine (EVM)
5. Ethereum Virtual Machine (EVM) Message Calls

Installation and Technical Requirements

1. [Overview] Installing Solidity Compiler
2. How to Install the Solidity Compiler with npm?
3. How to Install the Solidity Compiler via Docker on Ubuntu?
4. How to Install the Solidity Compiler via Source Code Compilation?
5. How to Install the Solidity Compiler via Static Binary and Linux Packages

Guided Example Smart Contracts

1. [Overview] Top 5 Solidity Smart Contract Examples for Learning
2. Example 1: How Does the Solidity Voting Smart Contract Work?
3. Example 2: Simple Open Auction (Explained)
4. Example 3: Mastering the Solidity Blind Auction Contract
5. Example 4: Safe Remote Purchase
6. Example 5: Understanding Modular Contracts

Solidity Layout

1. Solidity File Layout – SPDX License ID and Version Pragmas
2. Solidity Layout – Pragmas, Importing, and Comments

Solidity Language Elements

1. [Overview] Seven Simple Solidity Blocks to Build Your dApp (State Variables, Functions, Modifiers, Events, Errors, Structs, Enums)
2. Boolean and Integer Types
3. Fixed Point Numbers and Address Types
4. Contract Types, Byte Arrays, and {Address, Int, Rational} Literals
5. String Types, Unicode/Hex Literals, and Enums
6. User-Defined Value Types
7. Function Types

Problem Formulation and Solution Overview

If you print all values from a dictionary in Python using print(dict.values()), Python returns a dict_values object, a view of the dictionary values. The representation prints the keys enclosed in a weird dict_values(...), for example: dict_values([1, 2, 3]).

Here’s an example:

my_dict = {'name': 'Carl', 'age': 42, 'income': 100000}

print(my_dict.values())

# dict_values(['Carl', 42, 100000])

There are multiple ways to change the string representation of the values, so that the print() output doesn’t yield the strange dict_values view object.

Method 1: Convert to List

An easy way to obtain a pretty output when printing the dictionary values without dict_values(...) representation is to convert the dict_value object to a list using the list() built-in function. For instance, print(list(my_dict.value())) prints the dictionary values as a simple list.

Here’s an example:

my_dict = {'name': 'Carl', 'age': 42, 'income': 100000}

print(list(my_dict.values()))

# ['Carl', 42, 100000]

So far, so simple. Read on to learn or recap some important Python features and improve your skills. There are many paths to Rome!

Method 2: Unpacking

An easy and Pythonic way to print a dictionary without the dict_values prefix is to unpack all values into the print() function using the asterisk operator. This works because the print() function allows an arbitrary number of values as input. It prints those values separated by a single whitespace character per default.

Here’s an example:

my_dict = {'name': 'Carl', 'age': 42, 'income': 100000}

print(*my_dict.values())

# Carl 42 100000

It cannot get any more concise, frankly.

Of course, you can change the separator and end arguments accordingly to obtain more control of the output:

my_dict = {'name': 'Carl', 'age': 42, 'income': 100000}

print(*my_dict.values(), sep='\n', end='\nThe End')

Output:

Carl

42

100000

The End

Do you need even greater flexibility than this? No problem! See here:

Method 3: String Join Function and Generator Expression

To convert the dictionary values to a single string object without 'dict_values' in it and with maximal control, you can use the string.join() function in combination with a generator expression and the built-in str() function.

Here’s an example:

my_dict = {'name': 'Carl', 'age': 42, 'income': 100000}

print(', '.join(str(x) for x in my_dict.values()))

# Carl, 42, 100000

Note: You can replace the comma ',' with your desired separator character and modify the representation of each individual element by modifying the expression str(x) of the generator expression to something arbitrary complicated.

See here for something crazy that wouldn’t make any sense:

my_dict = {'name': 'Carl', 'age': 42, 'income': 100000}

print(' | '.join('x' + str(x) + 'x' for x in my_dict.values()))

# xCarlx | x42x | x100000x

Note that you could also use the repr() function instead of the str() function in this example—it wouldn’t matter too much.

Finally, I’d recommend you check out this tutorial to learn more how generator expressions work—many Python beginners struggle with this concept even though it’s ubiquitous in expert coders’ code bases.

Recommended Tutorial: Understanding One-Line Generators in Python

Google Sheets API provides services of to read and write a Google spreadsheet document.

This tutorial is for reading data from Google sheets and displaying them in the UI with JavaScript. Only JavaScript is used without any plugins or dependencies.

Steps to access Google Sheets

It requires the following steps to achieve this.

1. Get OAuth Credentials and API keys and configure them into an application.
2. Authenticate and Authorise the app to allow accessing Google sheets.
3. Read spreadsheet data and store it in an array.
4. Parse response data and display them on the UI.

Steps 1 and 2 are common for all Google JavaScript API services. When uploading files to Google Drive via JavaScript API, we have seen it.

We have also seen how to upload to Google Drive using PHP. It doesn’t need API Key. Instead, it does token-based authentication to get API access.

Step 1: Get OAuth Credentials and API keys and configure them into an application

In this step, it needs to create a developer’s web client app to get the client id and the API keys. For that, it requires the following setting should be enabled with the developer’s dashboard.

1. Login to the Google Developers console and create a web client.
2. Enable Google Sheets API from the gallery of Google APIs.
3. Configure OAuth content screen to set the app details
4. Click OAuth credentials and get the app client id and secret key.
5. Set the scope on which the program going to access the spreadsheet.
6. Get the API key to authenticate and authorize the app to access the Google Spreadsheet API service.

Note: The secret key will be used for server-side implementation, but not in this JavaScript example.

Required scope to access the spreadsheet data

The following scopes should be selected to read the Google Spreadsheets via a program.

• …auth/spreadsheets – to read, edit, create and delete Spreadsheets.
• …auth/spreadsheets.readonly – to read Spreadsheets.
• …auth/drive – to read, edit, create and delete Drive files.
• …auth/drive.readonly – to read Drive files
• …auth/drive.file – to read, edit, create and delete a specific Drive files belongs to the app gets authorized.

Step 2: Authenticate and Authorise the app to allow accessing Google sheets

Authorization is the process of the client signing into the Google API to access its services.

On clicking an “Authorize” button, it calls authorizeGoogleAccess() function created for this example.

This function shows a content screen for the end user to allow access. Then, it receives the access token in a callback handler defined in this function.

Step 3: Read spreadsheet data and store it in an array

Once access is permitted, the callback will invoke the script to access an existing Google spreadsheet.

The listMajors() function specifies a particular spreadsheet id to be accessed. This function uses JavaScript gapi instance to get the spreadsheet data.

Step 4: Parse response data and display them on the UI

After getting the response data from the API endpoint, this script parses the resultant object array.

It prepares the output HTML with the spreadsheet data and displays them to the target element.

If anything strange with the response, it shows the “No records found” message in the browser.

A complete code: Accessing Google Spreadsheets via JavaScript

The following script contains the HTML to show either “Authorize” or the two “Refresh” and “Signout” buttons. Those buttons’ display mode is based on the state of authorization to access the Google Spreadsheet API.

The example code includes the JavaScript library to make use of the required Google API services.

The JavaScript has the configuration to pin the API key and OAuth client id in a right place. This configuration is used to proceed with the steps 2, 3 and 4 we have seen above.

<!DOCTYPE html>

<html>

<head>

<title>Google Sheets JavaScript API Spreadsheet Tutorial</title>

<link rel='stylesheet' href='style.css' type='text/css' />

<link rel='stylesheet' href='form.css' type='text/css' />

</head>

<body> <div class="phppot-container"> <h1>Google Sheets JavaScript API Spreadsheet Tutorial</h1> <p>This tutorial is to help you learn on how to read Google Sheets (spreadsheet) using JavaScript Google API.</p> <button id="authorize_btn" on‌click="authorizeGoogleAccess()">Authorize Google Sheets Access</button> <button id="signout_btn" on‌click="signoutGoogle()">Sign Out</button> <pre id="content"></pre> </div> <script async defer src="https://apis.google.com/js/api.js" on‌load="gapiLoaded()"></script> <script async defer src="https://accounts.google.com/gsi/client" on‌load="gisLoaded()"></script>

</body>

</html>

// You should set your Google client ID and Google API key

const GOOGLE_CLIENT_ID = '';

const GOOGLE_API_KEY = '';

// const DISCOVERY_DOC = 'https://sheets.googleapis.com/$discovery/rest?version=v4'; // Authorization scope should be declared for spreadsheet handing

// multiple scope can he included separated by space

const SCOPES = 'https://www.googleapis.com/auth/spreadsheets.readonly'; let tokenClient;

let gapiInited = false;

let gisInited = false;

document.getElementById('authorize_btn').style.visibility = 'hidden';

document.getElementById('signout_btn').style.visibility = 'hidden'; /** * Callback after api.js is loaded. */

function gapiLoaded() { gapi.load('client', intializeGapiClient);

} /** * Callback after the Google API client is loaded. Loads the * discovery doc to initialize the API. */

async function intializeGapiClient() { await gapi.client.init({ apiKey: GOOGLE_API_KEY, discoveryDocs: [DISCOVERY_DOC], }); gapiInited = true; maybeEnableButtons();

} /** * Callback after Google Identity Services are loaded. */

function gisLoaded() { tokenClient = google.accounts.oauth2.initTokenClient({ client_id: GOOGLE_CLIENT_ID, scope: SCOPES, callback: '', // defined later }); gisInited = true; maybeEnableButtons();

} /** * Enables user interaction after all libraries are loaded. */

function maybeEnableButtons() { if (gapiInited && gisInited) { document.getElementById('authorize_btn').style.visibility = 'visible'; }

} /** * Sign in the user upon button click. */

function authorizeGoogleAccess() { tokenClient.callback = async (resp) => { if (resp.error !== undefined) { throw (resp); } document.getElementById('signout_btn').style.visibility = 'visible'; document.getElementById('authorize_btn').innerText = 'Refresh'; await listMajors(); }; if (gapi.client.getToken() === null) { // Prompt the user to select a Google Account and ask for consent to share their data // when establishing a new session. tokenClient.requestAccessToken({ prompt: 'consent' }); } else { // Skip display of account chooser and consent dialog for an existing session. tokenClient.requestAccessToken({ prompt: '' }); }

} /** * Sign out the user upon button click. */

function signoutGoogle() { const token = gapi.client.getToken(); if (token !== null) { google.accounts.oauth2.revoke(token.access_token); gapi.client.setToken(''); document.getElementById('content').innerText = ''; document.getElementById('authorize_btn').innerText = 'Authorize'; document.getElementById('signout_btn').style.visibility = 'hidden'; }

} /** * Print the names and majors of students in a sample spreadsheet: * https://docs.google.com/spreadsheets/d/1...Thvas/edit */

async function listMajors() { let response; try { // Fetch first 10 files response = await gapi.client.sheets.spreadsheets.values.get({ spreadsheetId: '', range: 'Sheet1!A2:D', }); } catch (err) { document.getElementById('content').innerText = err.message; return; } const range = response.result; if (!range || !range.values || range.values.length == 0) { document.getElementById('content').innerText = 'No values found.'; return; } const output = range.values.reduce( (str, row) => `${str}${row[0]}, ${row[2]}\n`, 'Birds, Insects:\n'); document.getElementById('content').innerText = output;

}

Source and output of this example

The spreadsheet shown in this screenshot is the source of this program to access its data.

The JavaScript example reads the spreadsheet and displays the Birds and the Insects column data in the UI.

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