add multicall

multicall/constants.py

@@ -9,7 +9,7 @@ class Network(IntEnum):
     xDai = 100
 
 
-MULTICALL_ADDRESS = {
+MULTICALL_ADDRESSES = {
     Network.Mainnet: '0xeefBa1e63905eF1D7ACbA5a8513c70307C1cE441',
     Network.Kovan: '0x2cc8688C5f75E365aaEEb4ea8D6a480405A48D2A',
     Network.Rinkeby: '0x42Ad527de7d4e9d9d011aC45B31D8551f8Fe9821',

multicall/multicall.py

@@ -0,0 +1,23 @@
+from typing import List
+
+from web3.auto import w3
+
+from multicall import Call
+from multicall.constants import MULTICALL_ADDRESSES
+
+
+class Multicall:
+    def __init__(self, calls: List[Call]):
+        self.calls = calls
+
+    def __call__(self):
+        aggregate = Call(
+            MULTICALL_ADDRESSES[w3.eth.chainId],
+            'aggregate((address,bytes)[])(uint256,bytes[])',
+        )
+        args = [[[call.target, call.data] for call in self.calls]]
+        block, outputs = aggregate(args)
+        result = {}
+        for call, output in zip(self.calls, outputs):
+            result.update(call.decode_output(output))
+        return result

tests/test_multicall.py

@@ -0,0 +1,21 @@
+from multicall import Call, Multicall
+
+CHAI = '0x06AF07097C9Eeb7fD685c692751D5C66dB49c215'
+
+
+def from_wei(val):
+    return val / 1e18
+
+
+def from_ray(val):
+    return val / 1e27
+
+
+def test_multicall():
+    multi = Multicall([
+        Call(CHAI, 'totalSupply()(uint256)', [['supply', from_wei]]),
+        Call(CHAI, ['balanceOf(address)(uint256)', CHAI], [['balance', from_ray]]),
+    ])
+    result = multi()
+    assert isinstance(result['supply'], float)
+    assert isinstance(result['balance'], float)

tests/test_signature.py

@@ -1,4 +1,4 @@
-from eth_abi import encode_abi, decode_abi
+from eth_abi import encode_abi
 from multicall import Signature
 
 args = ((1, 2, 3), '0x' + 'f' * 40, b'data')