Developing a Cryptocurrency Wallet with Python Web3, Streamlit, and Ganache Local Blockchain

Table of Contents:

1. Streamlit Krypto Jobs Application Usage

2. Running the Streamlit Demo

3. App Usage Instructions

Background

You work at a startup that is building a new and disruptive platform called KryptoJobs2Go. KryptoJobs2Go is an application that its customers can use to find fintech professionals from among a list of candidates, hire them, and pay them. As KryptoJobs2Go’s lead developer, you have been tasked with integrating the Ethereum blockchain network into the application in order to enable your customers to instantly pay the fintech professionals whom they hire with cryptocurrency.

In this Challenge, you will complete the code that enables your customers to send cryptocurrency payments to fintech professionals. To develop the code and test it out, you will assume the perspective of a KryptoJobs2Go customer who is using the application to find a fintech professional and pay them for their work.

What You're Creating

To complete this Challenge, you will use two Python files, both of which are contained in the starter folder.

The first file that you will use is called krypto_jobs.py. It contains the code associated with the web interface of your application. The code included in this file is compatible with the Streamlit library. You will write all of your code for this Challenge in this file.

The second file that you will use is called crypto_wallet.py. This file contains the Ethereum transaction functions that you have created throughout this module’s lessons. By using import statements, you will integrate the crypto_wallet.py Python script into the KryptoJobs2Go interface program that is found in the krypto_jobs.py file.

Integrating these two files will allow you to automate the tasks associated with generating a digital wallet, accessing Ethereum account balances, and signing and sending transactions via a personal Ethereum blockchain called Ganache.

Specifically, you will assume the perspective of a KryptoJobs2Go customer in order to do the following:

• Generate a new Ethereum account instance by using the mnemonic seed phrase provided by Ganache.

• Fetch and display the account balance associated with your Ethereum account address.

• Calculate the total value of an Ethereum transaction, including the gas estimate, that pays a KryptoJobs2Go candidate for their work.

• Digitally sign a transaction that pays a KryptoJobs2Go candidate, and send this transaction to the Ganache blockchain.

• Review the transaction hash code associated with the validated blockchain transaction.

Once you receive the transaction’s hash code, you will navigate to the Transactions section of Ganache to review the blockchain transaction details. To confirm that you have successfully created the transaction, you will save screenshots to the README.md file of your GitHub repository for this Challenge assignment.

Instructions

The steps for this challenge are broken out into the following sections:

• Import Ethereum Transaction Functions into the KryptoJobs2Go Application
• Sign and Execute a Payment Transaction
• Inspect the Transaction on Ganache

Step 1: Import Ethereum Transaction Functions into the KryptoJobs2Go Application

In this section, you'll import several functions from the crypto_wallet.py script into the file krypto_jobs.py, which contains code for KryptoJobs2Go’s customer interface, in order to add wallet operations to the application. For this section, you will assume the perspective of a KryptoJobs2Go customer (i.e., you’ll provide your Ethereum wallet and account information to the application).

Complete the following steps:

1. Review the code contained in the crypto_wallet.py script file. Note that the Ethereum transaction functions that you have built throughout this module—including wallet, wallet.derive_acount, get_balance, fromWei, estimateGas, sendRawTransaction, and others—have now been incorporated into Python functions that allow you to automate the process of accessing them.

2. Add your mnemonic seed phrase (provided by Ganache) to the starter code’s SAMPLE.env file. When the information has been added, rename the file .env.

3. Open the krypto_jobs.py file. Toward the top of the file, after the import statements that are provided, import the following functions from the crypto_wallet.py file:

   • generate_account

   • get_balance

   • send_transaction

4. Within the Streamlit sidebar section of code, create a variable named account. Set this variable equal to a call on the generate_account function. This function will create the KryptoJobs2Go customer’s (in this case, your) HD wallet and Ethereum account.

5. Within this same section of the krypto_jobs.py file, define a new st.sidebar.write function that will display the balance of the customer’s account. Inside this function, call the get_balance function and pass it your Ethereum account.address.

Step 2: Sign and Execute a Payment Transaction

Next, you'll write the code that will calculate a fintech professional’s wage, in ether, based on the worker’s hourly rate and the number of hours that they work for a customer. (The fintech professionals’ hourly rates are provided in the candidate_database that is found in krypto_jobs.py.)

You will then write code that uses the calculated wage value to send a transaction that pays the worker. This code should allow the KryptoJobs2Go customer to authorize the transaction with their digital signature. For the purpose of testing out this application, you will use your own Ethereum account information as the customer account information.

To accomplish all of this, complete the following steps:

1. KryptoJobs2Go customers will select a fintech professional from the application interface’s drop-down menu, and then input the amount of time for which they’ll hire the worker. Code the application so that once a customer completes these steps, the application will calculate the amount that the worker will be paid in ether. To do so, complete the following steps:

   • Write the equation that calculates the candidate’s wage. This equation should assess the candidate’s hourly rate from the candidate database (candidate_database[person][3]) and then multiply this hourly rate by the value of the hours variable. Save this calculation’s output as a variable named wage.

   • Write the wage variable to the Streamlit sidebar by using st.sidebar.write.

2. Now that the application can calculate a candidate’s wage, write the code that will allow a customer (you, in this case) to send an Ethereum blockchain transaction that pays the hired candidate. To accomplish this, locate the code that reads if st.sidebar.button("Send Transaction"). You’ll need to add logic to this if statement that sends the appropriate information to the send_transaction function (which you imported from the crypto_wallet script file). Inside the if statement, add the following functionality:

   • Call the send_transaction function and pass it three parameters:

   • Your Ethereum account information. (Remember that this account instance was created when the generate_account function was called.) From the account instance, the application will be able to access the account.address information that is needed to populate the from data attribute in the raw transaction.

   • The candidate_address (which will be created and identified in the sidebar when a customer selects a candidate). This will populate the to data attribute in the raw transaction.

   • The wage value. This will be passed to the toWei function to determine the wei value of the payment in the raw transaction.

   • Save the transaction hash that the send_transaction function returns as a variable named transaction_hash, and have it display on the application’s web interface.

Step 3: Inspect the Transaction

Now it's time to put it all together and test the KryptoJobs2Go application with your newly integrated Ethereum wallet. You will send a test transaction by using the application’s web interface, and then look up the resulting transaction in Ganache. To do so, complete the following steps:

1. From your terminal, navigate to the project folder that contains your .env file and the krypto_jobs.py and crypto_wallet.py files. Be sure to activate your Conda dev environment if it is not already active.

2. To launch the Streamlit application, type streamlit run krypto_jobs.py.

3. On the resulting webpage, select a candidate that you would like to hire from the appropriate drop-down menu. Then, enter the number of hours that you would like to hire them for. (Remember, you do not have a lot of ether in your account, so you cannot hire them for long!)

4. Click the Send Transaction button to sign and send the transaction with your Ethereum account information. Navigate to the Transactions section of Ganache.

   • Take a screenshot of your address balance and history on Ganache. Save this screenshot to the README.md file of your GitHub repository for this Challenge assignment.

   • Take a screenshot of the transaction details on Ganache. Save this screenshot to the README.md file of your GitHub repository for this Challenge assignment.

5. Return to the original transaction, and click the transaction’s To address.

• Take a screenshot of the recipient’s address balance and history from your Ganache application. Save this screenshot to the README.md file of your GitHub repository for this Challenge assignment.

Streamlit Krypto Jobs Application Usage:

Streamlit_CryptoWalletUsage_2.mp4

• This application enables users who are in need of fintech professionals to hire and provide payment in crypto-currency.

• Using Python's Web3 package, I was able to integerate the Ethereum blockchain network into the application which was connected to a local blockchain-ledger on Ganache to test sending & receiving payments on the blockchain.

• This application also utilizes Streamlit to display a clean user interface. The video snippet above demonstrates the usage of the application and displays how the user can send crypto currency payments to fintech professionals with just a few inputs.

Running the Streamlit Demo:

    Activate development environment that includes the following packages: 

    conda activate <environment>

    pip install bip44 
    pip install web3==5.17
    pip install eth-tester==0.5.0b3
    pip install mnemonic

    Download Ganache:
    
    https://trufflesuite.com/ganache/

    Run Streamlit Demo: 

    streamlit run krypto_jobs.py

    [make sure to create an .env file holding your own local Ganache Blockchain Mnemonic Phrase]

App Usage Instructions & Outputs:

1. Select a Fintech Professional to hire

2. Enter the number of hours you want to hire the Fintech Professional for

3. Review the output

   • Candidate Name, Hourly Rate, & Ethereum address
   • Total Wage in Ether provided

4. Click Send Transaction

5. Review the output

   • Validated transaction hash
   • Open Ganache and review transaction output
     • Balance
     • Sender address
     • To address
     • TX hash
     • Gas used
     • Value in ETH sent

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