diff --git a/examples/filter_events_example.ipynb b/examples/filter_events_example.ipynb
index 2c97985..1b98288 100644
--- a/examples/filter_events_example.ipynb
+++ b/examples/filter_events_example.ipynb
@@ -1053,7 +1053,7 @@
    "source": [
     "lhe_data = data_path(\"pylhe-drell-yan-ll-lhe.gz\")\n",
     "with gzip.open(lhe_data) as f:\n",
-    "    for i in range(1000):\n",
+    "    for _ in range(1000):\n",
     "        print(f.readline())"
    ]
   },
diff --git a/examples/write_monte_carlo_example.ipynb b/examples/write_monte_carlo_example.ipynb
index 9334559..30a74bf 100644
--- a/examples/write_monte_carlo_example.ipynb
+++ b/examples/write_monte_carlo_example.ipynb
@@ -62,7 +62,7 @@
     "# https://equation-database.readthedocs.io/en/latest/_autosummary/equation_database.isbn_9780471887416.html#equation_database.isbn_9780471887416.equation_6_32\n",
     "\n",
     "\n",
-    "def dsigma(s, theta, phi):\n",
+    "def dsigma(s, theta, _phi):\n",
     "    return (math.cos(theta) ** 2 + 1) / 4 * alpha**2 / s"
    ]
   },
@@ -174,7 +174,7 @@
     "num_samples = 100000\n",
     "integ = 0.0\n",
     "lheevents = []\n",
-    "for i in range(num_samples):\n",
+    "for _i in range(num_samples):\n",
     "    theta = random.uniform(theta_min, theta_max)\n",
     "    phi = random.uniform(phi_min, phi_max)\n",
     "    sig = (\n",
diff --git a/src/pylhe/__init__.py b/src/pylhe/__init__.py
index 644ea22..d393b9f 100644
--- a/src/pylhe/__init__.py
+++ b/src/pylhe/__init__.py
@@ -1,7 +1,7 @@
 import gzip
 import io
 import xml.etree.ElementTree as ET
-from typing import Iterable
+from typing import Iterable, Optional
 
 import graphviz
 from particle import latex_to_html_name
@@ -367,7 +367,9 @@ def fromstring(cls, string):
 
 
 class LHEFile:
-    def __init__(self, init: LHEInit = None, events: Iterable[LHEEvent] = None):
+    def __init__(
+        self, init: LHEInit = None, events: Optional[Iterable[LHEEvent]] = None
+    ):
         self.init = init
         self.events = events