Interact with the top 20 erc20 tokens right from your terminal.
In this guide, we'll use ethPM & web3.py to instantly interact with any of the top 20 erc20 tokens with a couple lines of code from your terminal, without copy/pasting a single ABI!! In this example we'll be using the DAI token, but all top 20 tokens are available as ethPM packages on the erc20 package registry. All you will need for this tutorial is an Infura API key, if you don't already have one, you can get one here.
tl;dr
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>from web3.auto.infura import w3
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> w3.pm.set_registry('erc20.snakecharmers.eth')
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> dai_pkg = w3.pm.get_package("dai-dai")
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> dai = dai_pkg.deployments.get_instance("DSToken")
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​
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# Now you can interact with dai like any erc20 tokens.
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> dai.functions.totalSupply().call()
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78512091351850936215202968
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Step by Step
Install Python
For this tutorial, you must have Python 3.6+ installed on your machine. Check out this tutorial for more info.
Create your directory & virtual environment
Virtual environments are best practice in Python world, so let's follow suit.
Some setup is required in web3.py before we can play with our Dai. The enable_unstable_package_management_api flag is a temporary security measure. While web3.pm is in alpha, we want to be extra sure that users understand the API might change in the future. This precaution will be removed once the web3.pm API stabilizes in the next web3.py release.
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>from web3.auto.infura import w3
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> w3.enable_unstable_package_management_api()
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Set the active registry
We'll be using the erc20 registry located on the Ethereum mainnet at under the ENS name erc20.snakecharmers.eth which resolves to the address 0x16763EaE3709e47eE6140507Ff84A61c23B0098A . You can explore the various erc20 tokens available on this registry on the ethPM explorer. Since our w3 instance is already connected to mainnet, all we have to do is set the registry.
Since the contract instance data is contained within the dai-dai package, it's quite simple to grab a contract instance class representing the Dai token contract. We will use the contract type DSToken to grab the Dai instance.
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> dai = dai_package.deployments.get_instance("DSToken")
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Sidenote: dai_package is an instance of py-ethpm's Package class. This class automatically filters available deployments that live on the connected w3 instance. To access a package's deployments that live on a different blockchain, you can pass a new w3 instance to Package.update_w3().
Play with your Dai!
Now we have a contract instance representing the Dai contract. We can interact with any of its available functions. Of course, to send Dai, you must first own Dai!
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> dai.functions.totalSupply().call()
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78512091351850936215202968
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​
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> dai.functions.send("me.eth").transact()
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You can follow these steps to interact with any of the erc20 token packages available in the connected registry.
Generate your own Etherscan verified contract package
Each package in the above erc20 registry was created using the ethPM CLI's create command in combination with its corresponding Etherscan URI. If you're the curious type, and want to re-generate the package locally, these steps can be used to package up any of Etherscan's verified contracts on any blockchain.
To generate an Etherscan verified contract package, we'll use ethPM CLI. So you'll need to have that installed on your machine. Steps for how to get setup can be found here.
Next, you'll need an Etherscan API key. If you don't already have an Etherscan API key, you can grab one here. Then set it as the following environment variable.
ethPM CLI uses Etherscan URIs to identify the target verified contract. Once you have the address and chain ID of your verified contract, the URI simply follows this scheme.
Then, all you need to do is execute the following command, and the CLI will package up the verified contract, and write it to your local _ethpm_packages/ directory. You can use any package name or package version that makes sense.
By default, this command will write the generated manifest to an _ethpm_packages/ directory in the current working directory. If no such directory is found, it will automatically generate one. You can also pass the command an --ethpm-dir flag to target a specific directory.
You can check out your newly created package by exploring the _ethpm_packages/ directory, and you will also see it listed by calling ethpm list.