uniswap-python · ErikBjare · Sep 8, 2023 · Mar 18, 2023 · Mar 18, 2023 · Jul 21, 2023
diff --git a/examples/price_impact.py b/examples/price_impact.py
@@ -27,7 +27,7 @@ def usdt_to_vxv_v2():
 
     # Compare the results with the output of:
     # https://app.uniswap.org/#/swap?use=v2&inputCurrency=0xdac17f958d2ee523a2206206994597c13d831ec7&outputCurrency=0x7d29a64504629172a429e64183d6673b9dacbfce
-    qty = 10 * 10 ** 8
+    qty = 10 * 10**8
 
     # price = uniswap.get_price_input(usdt, vxv, qty, route=route) / 10 ** 18
     # print(price)
@@ -38,7 +38,7 @@ def usdt_to_vxv_v2():
     #       The slippage for v3 (in example below) returns correct results.
     print(f"Impact for buying VXV on v2 with {qty / 10**8} USDT:  {_perc(impact)}")
 
-    qty = 13900 * 10 ** 8
+    qty = 13900 * 10**8
     impact = uniswap.estimate_price_impact(usdt, vxv, qty, route=route)
     print(f"Impact for buying VXV on v2 with {qty / 10**8} USDT:  {_perc(impact)}")
 
@@ -49,11 +49,11 @@ def eth_to_vxv_v3():
 
     # Compare the results with the output of:
     # https://app.uniswap.org/#/swap?use=v3&inputCurrency=ETH&outputCurrency=0x7d29a64504629172a429e64183d6673b9dacbfce
-    qty = 1 * 10 ** 18
+    qty = 1 * 10**18
     impact = uniswap.estimate_price_impact(eth, vxv, qty, fee=10000)
     print(f"Impact for buying VXV on v3 with {qty / 10**18} ETH:  {_perc(impact)}")
 
-    qty = 100 * 10 ** 18
+    qty = 100 * 10**18
     impact = uniswap.estimate_price_impact(eth, vxv, qty, fee=10000)
     print(f"Impact for buying VXV on v3 with {qty / 10**18} ETH:  {_perc(impact)}")
 

diff --git a/tests/test_uniswap.py b/tests/test_uniswap.py
@@ -69,6 +69,7 @@ def test_assets(client: Uniswap):
     """
     tokens = get_tokens(client.netname)
 
+
     for token_name, amount in [
         ("DAI", 10_000 * ONE_DAI),
         ("USDC", 10_000 * ONE_USDC),
@@ -133,6 +134,13 @@ def does_not_raise():
     yield
 
 
+
+ONE_ETH = 10**18
+ONE_USDC = 10**6
+
+ZERO_ADDRESS = "0x0000000000000000000000000000000000000000"
+
+
 # TODO: Change pytest.param(..., mark=pytest.mark.xfail) to the expectation/raises method
 @pytest.mark.usefixtures("client", "web3")
 class TestUniswap(object):

diff --git a/uniswap/constants.py b/uniswap/constants.py
@@ -78,7 +78,12 @@
 MAX_TICK = -MIN_TICK
 
 # Source: https://github.com/Uniswap/v3-core/blob/v1.0.0/contracts/UniswapV3Factory.sol#L26-L31
-_tick_spacing = {100:1, 500: 10, 3_000: 60, 10_000: 200}
+_tick_spacing = {100: 1, 500: 10, 3_000: 60, 10_000: 200}
 
 # Derived from (MIN_TICK//tick_spacing) >> 8 and (MAX_TICK//tick_spacing) >> 8
-_tick_bitmap_range = {100:(-3466, 3465), 500: (-347, 346), 3_000: (-58, 57), 10_000: (-18, 17)}
+_tick_bitmap_range = {
+    100: (-3466, 3465),
+    500: (-347, 346),
+    3_000: (-58, 57),
+    10_000: (-18, 17),
+}
diff --git a/uniswap/uniswap.py b/uniswap/uniswap.py
@@ -33,6 +33,7 @@
     encode_sqrt_ratioX96,
     is_same_address,
     nearest_tick,
+    realised_fee_percentage,
 )
 from .decorators import supports, check_approval
 from .constants import (
@@ -1926,7 +1927,14 @@ def estimate_price_impact(
             cost_amount / (amount_in / (10 ** self.get_token(token_in).decimals))
         ) / 10 ** self.get_token(token_out).decimals
 
-        return float((price_small - price_amount) / price_small)
+        # calculate and subtract the realised fees from the price impact. See:
+        # https://github.com/uniswap-python/uniswap-python/issues/310
+        # The fee calculation will need to be updated when adding support for the AutoRouter.
+        price_impact_with_fees = float((price_small - price_amount) / price_small)
+        fee_realised_percentage = realised_fee_percentage(fee, amount_in)
+        price_impact_real = price_impact_with_fees - fee_realised_percentage
+
+        return price_impact_real
 
     # ------ Exchange ------------------------------------------------------------------
     @supports([1, 2])

diff --git a/uniswap/util.py b/uniswap/util.py
@@ -126,3 +126,19 @@ def nearest_tick(tick: int, fee: int) -> int:
 def chunks(arr: Sequence[Any], n: int) -> Generator:
     for i in range(0, len(arr), n):
         yield arr[i : i + n]
+
+
+def fee_to_fraction(fee: int):
+    return fee / 1000000
+
+
+def realised_fee_percentage(fee: int, amount_in: int) -> float:
+    """
+    Calculate realised fee expressed as a percentage of the amount_in.
+    The realised fee is rounded up as fractional units cannot be used -
+        this correlates to how the fees are rounded by Uniswap.
+    """
+
+    fee_percentage = fee_to_fraction(fee)
+    fee_realised = math.ceil(amount_in * fee_percentage)
+    return fee_realised / amount_in