Add eth_gasPrice module

trinity/rpc/modules/eth.py

@@ -169,8 +169,31 @@ async def estimateGas(self, txn_dict: Dict[str, Any], at_block: Union[str, int])
         gas = self._chain.estimate_gas(transaction, header)
         return hex(gas)
 
-    async def gasPrice(self) -> int:
-        raise NotImplementedError()
+    async def gasPrice(self) -> str:
+        canonical_header = self._chain.get_canonical_head()
+        canonical_block = self._chain.get_block_by_header(canonical_header)
+
+        # Get the latest block having non-zero transactions
+        latest_block_having_transactions = canonical_block
+        while len(latest_block_having_transactions.transactions) != 0:
+            # Make the transactions_having_latest_block as its parent, since it has no transactions
+            latest_block_header_having_transactions = self._chain.get_block_header_by_hash(
+                latest_block_having_transactions.header.parent_hash
+            )
+            latest_block_having_transactions = self._chain.get_block_by_header(
+                latest_block_header_having_transactions
+            )
+
+        # Sum of all the gas_price in transactions of the block
+        block_overall_gas_price = 0
+        for transaction in latest_block_having_transactions.transactions:
+            block_overall_gas_price += transaction.gas_price
+
+        # Get the average
+        num_transactions_latest_block = len(latest_block_having_transactions.transactions)
+        block_average_gas_price = block_overall_gas_price // num_transactions_latest_block
+
+        return hex(block_average_gas_price)
 
     @format_params(decode_hex, to_int_if_hex)
     async def getBalance(self, address: Address, at_block: Union[str, int]) -> str: