web3 python sendTransaction error

Question

from web3 import *

etherscan_provider = Web3.HTTPProvider( 'https://api.etherscan.io/api')
w3 = Web3(etherscan_provider)


signed_txn = w3.eth.account.signTransaction(dict(
    gas = 2000000,
    gasPrice= 234567897654321,
    nonce=0,
    to='0xABA024480E6B9e92B7e3332a2a3eb104F183D18C',
    value= 100000,
    chainId = 1
),
'0x2850d0xxxxxxxxxxxxxxxxxxxxxxxxxx')


w3.eth.sendRawTransaction(signed_txn.rawTransaction)

Return

File "/root/eth/lib/python3.6/site-packages/eth_utils/conversions.py", line 142, in hexstr_if_str                                                                             
hexstr_or_primitive                                                                                                                                                         
ValueError: when sending a str, it must be a hex string. Got: 'Error! Missing Or invalid Module name'   

What's the problem?

Answer 1

The etherscan API is not a JSON-RPC-compatible API. If you want to use a remote node with web3, you can use something like Infura.

According to their documentation, there are ways to invoke the JSON-RPC methods, but they don't actually implement the API externally. For example, to get the latest block number in the JSON-RPC API, you would send a POST like this:

curl -X POST --data '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":83}' localhost:8545

(which web3.py does for you behind the scenes of w3.eth.blockNumber)

In the etherscan API, you would send a GET, like this:

curl https://api.etherscan.io/api?module=proxy&action=eth_blockNumber&apikey=YourApiKeyToken

The two APIs are simply different. It would be possible to create a new specialized EtherscanProvider to work inside web3.py, instead of the normal HTTPProvider, but it would take a bit of work.