Write "guide" in docs for ERC20 token interactions. #1170
Description
What was wrong?
Interactions with ERC20 tokens are a very common use case. Examples in the documentation would likely be a valuable resource.
There is an existing minimalistic guide here: https://github.com/ethereum/web3.py/blob/master/docs/examples.rst that only deals with read-only operations.
How can it be fixed?
Write a "guide" for interacting with an ERC20 token. It should probably include as much of the following as is viable.
- creation of the contract factory from the ERC20 ABI
- instantiation of a contract instance pointed at a specific token address
- querying account balances
- performing a direct
transfer(...)call - querying the approved spending balance for external transfers
- creating an approval for external transfers
- performing a
transferFromcall with an approved transfer.
And some additional things:
- The guide should probably operate on a local test chain and include basic deployment of an simple ERC20 token contract.
- Guide should ignore key management, assuming that the node is doing the signing.
- Guide should be fully doctested using a web3 instance attached to an in-memory testing chain.