diff --git a/Makefile b/Makefile
index fd99cbbbf..d3be82a72 100644
--- a/Makefile
+++ b/Makefile
@@ -6,6 +6,7 @@ documentation:
 	python docs/add_plotly_to_book.py docs/_build
 
 format:
+	ruff check . --fix
 	ruff format .
 
 install:
diff --git a/changelog.d/add-ruff-linting.added.md b/changelog.d/add-ruff-linting.added.md
new file mode 100644
index 000000000..597070fb5
--- /dev/null
+++ b/changelog.d/add-ruff-linting.added.md
@@ -0,0 +1 @@
+Added ruff linting (ruff check) to Makefile format target with E, F, and I rule sets.
diff --git a/docs/usage/country.ipynb b/docs/usage/country.ipynb
index 5d49b73a6..691dbe2cb 100644
--- a/docs/usage/country.ipynb
+++ b/docs/usage/country.ipynb
@@ -16,11 +16,11 @@
    "outputs": [],
    "source": [
     "from policyengine_core.country_template import (\n",
-    "    CountryTaxBenefitSystem,  # Holds all policy-related data.\n",
-    "    Simulation,  # General purpose: enables users to simulate policy on new data.\n",
-    "    Microsimulation,  # Specific purpose: enables users to simulate policy on large datasets.\n",
     "    COUNTRY_DIR,  # Path to the country directory.\n",
     "    DATASETS,  # List of datasets available for this country (to use with `Microsimulation`).\n",
+    "    CountryTaxBenefitSystem,  # Holds all policy-related data.\n",
+    "    Microsimulation,  # Specific purpose: enables users to simulate policy on large datasets.\n",
+    "    Simulation,  # General purpose: enables users to simulate policy on new data.\n",
     ")"
    ]
   },
@@ -52,23 +52,16 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "import os\n",
-    "from typing import Dict, Type\n",
-    "from policyengine_core.data.dataset import Dataset\n",
-    "from policyengine_core.populations.population import Population\n",
-    "from policyengine_core.taxbenefitsystems import TaxBenefitSystem\n",
     "from policyengine_core.country_template import entities\n",
-    "from policyengine_core.country_template.situation_examples import couple\n",
-    "from policyengine_core.simulations import Simulation as CoreSimulation\n",
-    "from policyengine_core.simulations import (\n",
-    "    Microsimulation as CoreMicrosimulation,\n",
-    ")\n",
+    "from policyengine_core.country_template.constants import COUNTRY_DIR\n",
     "from policyengine_core.country_template.data.datasets.country_template_dataset import (\n",
     "    CountryTemplateDataset,\n",
     ")\n",
-    "from pathlib import Path\n",
-    "import logging\n",
-    "from policyengine_core.country_template.constants import COUNTRY_DIR\n",
+    "from policyengine_core.simulations import (\n",
+    "    Microsimulation as CoreMicrosimulation,\n",
+    ")\n",
+    "from policyengine_core.simulations import Simulation as CoreSimulation\n",
+    "from policyengine_core.taxbenefitsystems import TaxBenefitSystem\n",
     "\n",
     "DATASETS = [CountryTemplateDataset]  # Important: must be instantiated\n",
     "\n",
diff --git a/docs/usage/datasets.ipynb b/docs/usage/datasets.ipynb
index a7cfbce22..24d6cfa2d 100644
--- a/docs/usage/datasets.ipynb
+++ b/docs/usage/datasets.ipynb
@@ -32,7 +32,7 @@
    "source": [
     "from policyengine_core.country_template.constants import COUNTRY_DIR\n",
     "from policyengine_core.data import Dataset\n",
-    "from policyengine_core.periods import ETERNITY, MONTH, period\n",
+    "from policyengine_core.periods import ETERNITY, period\n",
     "\n",
     "\n",
     "class CountryTemplateDataset(Dataset):\n",
diff --git a/docs/usage/simulation.ipynb b/docs/usage/simulation.ipynb
index 66979a965..8add3e8b5 100644
--- a/docs/usage/simulation.ipynb
+++ b/docs/usage/simulation.ipynb
@@ -1044,7 +1044,8 @@
    ],
    "source": [
     "import plotly.express as px\n",
-    "from policyengine_core.charts import format_fig, display_fig, BLUE\n",
+    "\n",
+    "from policyengine_core.charts import BLUE, format_fig\n",
     "\n",
     "fig = (\n",
     "    px.line(\n",
diff --git a/policyengine_core/charts/__init__.py b/policyengine_core/charts/__init__.py
index f12564970..69c00d563 100644
--- a/policyengine_core/charts/__init__.py
+++ b/policyengine_core/charts/__init__.py
@@ -1,15 +1,14 @@
+from .api import *
+from .bar import *
 from .formatting import (
     BLUE,
     BLUE_COLOUR_SCALE,
-    DARK_GREEN,
-    LIGHT_GREEN,
     DARK_GRAY,
+    DARK_GREEN,
     GRAY,
     LIGHT_GRAY,
+    LIGHT_GREEN,
     WHITE,
-    format_fig,
     display_fig,
+    format_fig,
 )
-
-from .bar import *
-from .api import *
diff --git a/policyengine_core/charts/api.py b/policyengine_core/charts/api.py
index cddc2bf32..6fb9da460 100644
--- a/policyengine_core/charts/api.py
+++ b/policyengine_core/charts/api.py
@@ -1,12 +1,14 @@
-import requests
 import time
+
 import plotly.graph_objects as go
+import requests
+
 from .formatting import (
+    BLUE_LIGHT,
+    BLUE_PRIMARY,
     DARK_GRAY,
     MEDIUM_DARK_GRAY,
     WHITE,
-    BLUE_LIGHT,
-    BLUE_PRIMARY,
     format_fig,
 )
 
diff --git a/policyengine_core/charts/bar.py b/policyengine_core/charts/bar.py
index 03798cb0c..063c0f86a 100644
--- a/policyengine_core/charts/bar.py
+++ b/policyengine_core/charts/bar.py
@@ -1,9 +1,11 @@
+from typing import Callable
+
+import numpy as np
 import pandas as pd
-from .formatting import *
 import plotly.express as px
 from microdf import MicroSeries
-from typing import Callable
-import numpy as np
+
+from .formatting import *
 
 
 def bar_chart(
diff --git a/policyengine_core/commons/formulas.py b/policyengine_core/commons/formulas.py
index 425628d55..adca3f2fb 100644
--- a/policyengine_core/commons/formulas.py
+++ b/policyengine_core/commons/formulas.py
@@ -1,16 +1,13 @@
 import logging
 from typing import Any, Callable, Dict, List, Sequence, Type, TypeVar, Union
+from warnings import warn
 
 import numpy
 import numpy as np
 import pandas as pd
-from numpy import logical_not as not_
 from numpy import maximum as max_
 from numpy import minimum as min_
-from numpy import round as round_
-from numpy import select, where
-
-from warnings import warn
+from numpy import select
 
 from policyengine_core.parameters.parameter_node import ParameterNode
 from policyengine_core.periods.period_ import Period
@@ -18,8 +15,6 @@
 from policyengine_core.types import ArrayLike, ArrayType
 from policyengine_core.variables.variable import Variable
 
-import json
-
 T = TypeVar("T")
 
 
@@ -426,7 +421,7 @@ def sum_of_variables(variables: Union[List[str], str]) -> Callable:
     """
 
     warn(
-        f"Sum-of-variables formulas are deprecated- please use `adds` or `subtracts` instead."
+        "Sum-of-variables formulas are deprecated- please use `adds` or `subtracts` instead."
     )
 
     def sum_of_variables(entity, period, parameters):
diff --git a/policyengine_core/country_template/data/datasets/country_template_dataset.py b/policyengine_core/country_template/data/datasets/country_template_dataset.py
index d0ae21795..0abd45ef3 100644
--- a/policyengine_core/country_template/data/datasets/country_template_dataset.py
+++ b/policyengine_core/country_template/data/datasets/country_template_dataset.py
@@ -1,6 +1,6 @@
 from policyengine_core.country_template.constants import COUNTRY_DIR
 from policyengine_core.data import Dataset
-from policyengine_core.periods import ETERNITY, MONTH, period
+from policyengine_core.periods import ETERNITY, period
 
 
 class CountryTemplateDataset(Dataset):
diff --git a/policyengine_core/data/dataset.py b/policyengine_core/data/dataset.py
index 7caebb0c0..70478e5ab 100644
--- a/policyengine_core/data/dataset.py
+++ b/policyengine_core/data/dataset.py
@@ -1,19 +1,21 @@
+import os
+import shutil
+import sys
+import tempfile
 from pathlib import Path
-from typing import Dict, Union, List
+from typing import Dict, List, Union
+
 import h5py
 import numpy as np
 import pandas as pd
-import shutil
 import requests
-import os
-import tempfile
-from policyengine_core.tools.hugging_face import *
+
 from policyengine_core.tools.google_cloud import (
-    parse_gs_url,
     download_gcs_file,
+    parse_gs_url,
     upload_gcs_file,
 )
-import sys
+from policyengine_core.tools.hugging_face import *
 from policyengine_core.tools.win_file_manager import WindowsAtomicFileManager
 
 
diff --git a/policyengine_core/data_storage/in_memory_storage.py b/policyengine_core/data_storage/in_memory_storage.py
index a5e510b42..a87c6ff59 100644
--- a/policyengine_core/data_storage/in_memory_storage.py
+++ b/policyengine_core/data_storage/in_memory_storage.py
@@ -1,4 +1,4 @@
-from typing import Dict, Union
+from typing import Dict
 
 import numpy
 from numpy.typing import ArrayLike
diff --git a/policyengine_core/entities/helpers.py b/policyengine_core/entities/helpers.py
index bb0162ac0..c537f7de5 100644
--- a/policyengine_core/entities/helpers.py
+++ b/policyengine_core/entities/helpers.py
@@ -1,4 +1,4 @@
-from typing import List, Union
+from typing import List
 
 from policyengine_core import entities
 from policyengine_core.entities.entity import Entity
diff --git a/policyengine_core/enums/enum.py b/policyengine_core/enums/enum.py
index 0522cdaf5..8cfdfea4b 100644
--- a/policyengine_core/enums/enum.py
+++ b/policyengine_core/enums/enum.py
@@ -1,9 +1,12 @@
 from __future__ import annotations
+
 import enum
 import logging
 from functools import lru_cache
 from typing import Tuple, Union
+
 import numpy as np
+
 from .config import ENUM_ARRAY_DTYPE
 from .enum_array import EnumArray
 
diff --git a/policyengine_core/model_api.py b/policyengine_core/model_api.py
index 68f1f2dd4..87244c653 100644
--- a/policyengine_core/model_api.py
+++ b/policyengine_core/model_api.py
@@ -1,33 +1,5 @@
-from datetime import date
-
-from numpy import logical_not as not_
-from numpy import maximum as max_
-from numpy import minimum as min_
-from numpy import round as round_
-from numpy import select, where
-
-from policyengine_core.enums import Enum
-from policyengine_core.holders import (
-    set_input_dispatch_by_period,
-    set_input_divide_by_period,
-)
-from policyengine_core.parameters import (
-    Parameter,
-    ParameterNode,
-    ParameterScale,
-    ParameterScaleBracket,
-    load_parameter_file,
-)
-from policyengine_core.periods import DAY, ETERNITY, MONTH, YEAR, period
-from policyengine_core.populations import ADD, DIVIDE
-from policyengine_core.reforms import Reform
-from policyengine_core.simulations import (
-    calculate_output_add,
-    calculate_output_divide,
-)
 from policyengine_core.variables import (
     QuantityType,
-    Variable,
     VariableCategory,
 )
 
diff --git a/policyengine_core/parameters/__init__.py b/policyengine_core/parameters/__init__.py
index 29a5faa43..04ff45fb3 100644
--- a/policyengine_core/parameters/__init__.py
+++ b/policyengine_core/parameters/__init__.py
@@ -13,11 +13,11 @@
 )
 from .helpers import contains_nan, load_parameter_file
 from .operations import (
+    get_parameter,
     homogenize_parameter_structures,
     interpolate_parameters,
     propagate_parameter_metadata,
     uprate_parameters,
-    get_parameter,
 )
 from .parameter import Parameter
 from .parameter_at_instant import ParameterAtInstant
diff --git a/policyengine_core/parameters/operations/homogenize_parameters.py b/policyengine_core/parameters/operations/homogenize_parameters.py
index 6d2e830a7..6ce0f5540 100644
--- a/policyengine_core/parameters/operations/homogenize_parameters.py
+++ b/policyengine_core/parameters/operations/homogenize_parameters.py
@@ -1,5 +1,5 @@
 import logging
-from typing import Any, Dict, List, Type
+from typing import Any, Dict, List
 
 from policyengine_core.enums import Enum
 from policyengine_core.parameters.parameter import Parameter
diff --git a/policyengine_core/parameters/operations/propagate_parameter_metadata.py b/policyengine_core/parameters/operations/propagate_parameter_metadata.py
index de2925ad3..e23a94547 100644
--- a/policyengine_core/parameters/operations/propagate_parameter_metadata.py
+++ b/policyengine_core/parameters/operations/propagate_parameter_metadata.py
@@ -1,4 +1,3 @@
-from policyengine_core.parameters.parameter import Parameter
 from policyengine_core.parameters.parameter_node import ParameterNode
 
 
diff --git a/policyengine_core/parameters/operations/uprate_parameters.py b/policyengine_core/parameters/operations/uprate_parameters.py
index 415b9fbf9..2e639330a 100644
--- a/policyengine_core/parameters/operations/uprate_parameters.py
+++ b/policyengine_core/parameters/operations/uprate_parameters.py
@@ -1,11 +1,11 @@
-from numpy import ceil, floor
+from datetime import datetime
 
 # rrule is purposely imported this way to allow for programmatic
 # calling of rrule.YEARLY, rrule.MONTHLY, and rrule.DAILY
 from dateutil import rrule
-from dateutil.relativedelta import relativedelta
 from dateutil.parser import parse
-from datetime import datetime
+from dateutil.relativedelta import relativedelta
+from numpy import ceil, floor
 
 from policyengine_core.parameters.operations.get_parameter import get_parameter
 from policyengine_core.parameters.parameter import Parameter
@@ -14,7 +14,7 @@
 )
 from policyengine_core.parameters.parameter_node import ParameterNode
 from policyengine_core.parameters.parameter_scale import ParameterScale
-from policyengine_core.periods import instant, Instant
+from policyengine_core.periods import instant
 
 
 def uprate_parameters(root: ParameterNode) -> ParameterNode:
diff --git a/policyengine_core/parameters/parameter.py b/policyengine_core/parameters/parameter.py
index 50c3205f7..8b4dfa89c 100644
--- a/policyengine_core/parameters/parameter.py
+++ b/policyengine_core/parameters/parameter.py
@@ -2,14 +2,15 @@
 import os
 from typing import Dict, List, Optional
 
+from policyengine_core.commons.misc import empty_clone
 from policyengine_core.errors import ParameterParsingError
-from .at_instant_like import AtInstantLike
-from .parameter_at_instant import ParameterAtInstant
+from policyengine_core.periods import INSTANT_PATTERN
+from policyengine_core.periods import period as get_period
 
-from .helpers import _validate_parameter, _compose_name
+from .at_instant_like import AtInstantLike
 from .config import COMMON_KEYS
-from policyengine_core.commons.misc import empty_clone
-from policyengine_core.periods import INSTANT_PATTERN, period as get_period
+from .helpers import _compose_name, _validate_parameter
+from .parameter_at_instant import ParameterAtInstant
 
 
 class Parameter(AtInstantLike):
diff --git a/policyengine_core/parameters/parameter_node.py b/policyengine_core/parameters/parameter_node.py
index 94dbd88ff..e88ac65fe 100644
--- a/policyengine_core/parameters/parameter_node.py
+++ b/policyengine_core/parameters/parameter_node.py
@@ -1,24 +1,23 @@
 import copy
 import os
 import typing
-from typing import Iterable, List, Type, Union
+from typing import Iterable, Union
 
 from policyengine_core import commons, parameters, tools
-from policyengine_core.data_structures import Reference
 from policyengine_core.periods.instant_ import Instant
 from policyengine_core.tracers import TracingParameterNodeAtInstant
 
 from .at_instant_like import AtInstantLike
-from .parameter import Parameter
-from .parameter_node_at_instant import ParameterNodeAtInstant
 from .config import COMMON_KEYS, FILE_EXTENSIONS
 from .helpers import (
-    load_parameter_file,
     _compose_name,
-    _validate_parameter,
-    _parse_child,
     _load_yaml_file,
+    _parse_child,
+    _validate_parameter,
+    load_parameter_file,
 )
+from .parameter import Parameter
+from .parameter_node_at_instant import ParameterNodeAtInstant
 
 EXCLUDED_PARAMETER_CHILD_NAMES = ["reference", "__pycache__"]
 
diff --git a/policyengine_core/parameters/parameter_node_at_instant.py b/policyengine_core/parameters/parameter_node_at_instant.py
index 343e152dc..64152c7e7 100644
--- a/policyengine_core/parameters/parameter_node_at_instant.py
+++ b/policyengine_core/parameters/parameter_node_at_instant.py
@@ -1,5 +1,4 @@
 import os
-import sys
 from typing import TYPE_CHECKING, Iterable, Union
 
 import numpy
diff --git a/policyengine_core/parameters/parameter_scale_bracket.py b/policyengine_core/parameters/parameter_scale_bracket.py
index 703b25a77..2cbc12eb0 100644
--- a/policyengine_core/parameters/parameter_scale_bracket.py
+++ b/policyengine_core/parameters/parameter_scale_bracket.py
@@ -1,4 +1,5 @@
 from typing import Iterable
+
 from policyengine_core.parameters import Parameter, ParameterNode
 
 
diff --git a/policyengine_core/periods/period_.py b/policyengine_core/periods/period_.py
index fd58f69c0..3a235fe4d 100644
--- a/policyengine_core/periods/period_.py
+++ b/policyengine_core/periods/period_.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 import calendar
-from datetime import datetime, date, timedelta
+from datetime import date, datetime, timedelta
 from typing import List
 
 from policyengine_core import periods
diff --git a/policyengine_core/populations/group_population.py b/policyengine_core/populations/group_population.py
index c770ee751..8e7b6f890 100644
--- a/policyengine_core/populations/group_population.py
+++ b/policyengine_core/populations/group_population.py
@@ -1,4 +1,4 @@
-from typing import TYPE_CHECKING, Any, Callable
+from typing import TYPE_CHECKING, Any, Callable, Container, Optional
 
 import numpy
 from numpy.typing import ArrayLike
@@ -6,9 +6,8 @@
 from policyengine_core import projectors
 from policyengine_core.entities import Entity, Role
 from policyengine_core.enums import EnumArray
-from policyengine_core.populations.population import Population
 from policyengine_core.periods.period_ import Period
-from typing import Optional, Container
+from policyengine_core.populations.population import Population
 
 if TYPE_CHECKING:
     from policyengine_core.simulations import Simulation
diff --git a/policyengine_core/populations/population.py b/policyengine_core/populations/population.py
index fbce9dcbf..c03774643 100644
--- a/policyengine_core/populations/population.py
+++ b/policyengine_core/populations/population.py
@@ -1,5 +1,5 @@
 import traceback
-from typing import TYPE_CHECKING, Any, List, Optional, Container
+from typing import TYPE_CHECKING, Any, Container, List, Optional
 
 import numpy
 from numpy.typing import ArrayLike
diff --git a/policyengine_core/reforms/reform.py b/policyengine_core/reforms/reform.py
index 068cac240..672c1a6e9 100644
--- a/policyengine_core/reforms/reform.py
+++ b/policyengine_core/reforms/reform.py
@@ -1,20 +1,21 @@
 from __future__ import annotations
 
 import copy
-from typing import Callable, Union, TYPE_CHECKING
+from typing import TYPE_CHECKING, Callable, Union
 
-from policyengine_core.parameters import ParameterNode, Parameter
+from policyengine_core.parameters import Parameter, ParameterNode
 from policyengine_core.taxbenefitsystems import TaxBenefitSystem
 
 if TYPE_CHECKING:
     from policyengine_core.simulations import Simulation
+import requests
+
 from policyengine_core.periods import (
-    period as period_,
     instant as instant_,
-    Period,
 )
-
-import requests
+from policyengine_core.periods import (
+    period as period_,
+)
 
 
 class classproperty(object):
diff --git a/policyengine_core/scripts/policyengine_command.py b/policyengine_core/scripts/policyengine_command.py
index 7aa85c888..d240346f9 100644
--- a/policyengine_core/scripts/policyengine_command.py
+++ b/policyengine_core/scripts/policyengine_command.py
@@ -1,6 +1,5 @@
 import argparse
 import sys
-import warnings
 
 from policyengine_core.scripts import add_tax_benefit_system_arguments
 
diff --git a/policyengine_core/simulations/__init__.py b/policyengine_core/simulations/__init__.py
index c992f3a2b..03c5ba788 100644
--- a/policyengine_core/simulations/__init__.py
+++ b/policyengine_core/simulations/__init__.py
@@ -6,7 +6,7 @@
     check_type,
     transform_to_strict_syntax,
 )
+from .individual_sim import IndividualSim
 from .microsimulation import Microsimulation
 from .simulation import Simulation
 from .simulation_builder import SimulationBuilder
-from .individual_sim import IndividualSim
diff --git a/policyengine_core/simulations/individual_sim.py b/policyengine_core/simulations/individual_sim.py
index c00933c87..1438a79cb 100644
--- a/policyengine_core/simulations/individual_sim.py
+++ b/policyengine_core/simulations/individual_sim.py
@@ -3,14 +3,13 @@
 """
 
 from functools import partial
-from typing import Dict, List
 
 import numpy as np
 
 from policyengine_core.entities.entity import Entity
 from policyengine_core.periods import period
 from policyengine_core.reforms import Reform, set_parameter
-from policyengine_core.simulations import SimulationBuilder, Simulation
+from policyengine_core.simulations import Simulation, SimulationBuilder
 from policyengine_core.taxbenefitsystems.tax_benefit_system import (
     TaxBenefitSystem,
 )
diff --git a/policyengine_core/simulations/microsimulation.py b/policyengine_core/simulations/microsimulation.py
index 28410d044..8264d963b 100644
--- a/policyengine_core/simulations/microsimulation.py
+++ b/policyengine_core/simulations/microsimulation.py
@@ -1,8 +1,6 @@
-from typing import Dict, Type
-
-from microdf import MicroDataFrame, MicroSeries
 import numpy as np
-from policyengine_core.data.dataset import Dataset
+from microdf import MicroDataFrame, MicroSeries
+
 from policyengine_core.periods import Period
 from policyengine_core.periods import period as get_period
 from policyengine_core.periods.config import MONTH, YEAR
diff --git a/policyengine_core/simulations/simulation.py b/policyengine_core/simulations/simulation.py
index 8f79c3b70..f49781e89 100644
--- a/policyengine_core/simulations/simulation.py
+++ b/policyengine_core/simulations/simulation.py
@@ -1,11 +1,12 @@
+import json
+import random
 import tempfile
+from pathlib import Path
 from typing import TYPE_CHECKING, Any, Dict, List, Type, Union
 
 import numpy as np
 import pandas as pd
 from numpy.typing import ArrayLike
-import logging
-from pathlib import Path
 
 from policyengine_core import commons, periods
 from policyengine_core.data.dataset import Dataset
@@ -14,34 +15,29 @@
 from policyengine_core.errors import CycleError, SpiralError
 from policyengine_core.holders.holder import Holder
 from policyengine_core.periods import Period
-from policyengine_core.periods.config import ETERNITY, MONTH, YEAR
-from policyengine_core.periods.helpers import period
+from policyengine_core.periods.config import MONTH, YEAR
+from policyengine_core.tools.google_cloud import (
+    download_gcs_file,
+    parse_gs_url,
+)
+from policyengine_core.tools.hugging_face import *
 from policyengine_core.tracers import (
     FullTracer,
     SimpleTracer,
     TracingParameterNodeAtInstant,
 )
-import random
-from policyengine_core.tools.hugging_face import *
-from policyengine_core.tools.google_cloud import (
-    parse_gs_url,
-    download_gcs_file,
-)
-
-import json
 
 if TYPE_CHECKING:
     from policyengine_core.taxbenefitsystems import TaxBenefitSystem
 
 from policyengine_core.experimental import MemoryConfig
-from policyengine_core.populations import Population, GroupPopulation
-from policyengine_core.tracers import SimpleTracer
-from policyengine_core.variables import Variable, QuantityType
-from policyengine_core.reforms.reform import Reform
 from policyengine_core.parameters import get_parameter
+from policyengine_core.populations import GroupPopulation, Population
+from policyengine_core.reforms.reform import Reform
 from policyengine_core.simulations.simulation_macro_cache import (
     SimulationMacroCache,
 )
+from policyengine_core.variables import QuantityType, Variable
 
 
 class Simulation:
@@ -592,7 +588,7 @@ def _calculate(self, variable_name: str, period: Period = None) -> ArrayLike:
                 ]
             ):
                 return holder.default_array()
-        except Exception as e:
+        except Exception:
             pass
 
         # First look for a value already cached
@@ -735,7 +731,7 @@ def _calculate(self, variable_name: str, period: Period = None) -> ArrayLike:
 
         except SpiralError:
             array = holder.default_array()
-        except RecursionError as e:
+        except RecursionError:
             if isinstance(self.tracer, FullTracer):
                 self.tracer.print_computation_log()
             stack = self.tracer.stack
diff --git a/policyengine_core/simulations/simulation_builder.py b/policyengine_core/simulations/simulation_builder.py
index 628a478c4..09aba30fd 100644
--- a/policyengine_core/simulations/simulation_builder.py
+++ b/policyengine_core/simulations/simulation_builder.py
@@ -15,21 +15,22 @@
 )
 from policyengine_core.periods import Period
 from policyengine_core.populations import GroupPopulation, Population
-from policyengine_core.simulations.simulation import Simulation
 from policyengine_core.simulations.helpers import (
-    check_type,
     _get_person_count,
+    check_type,
     transform_to_strict_syntax,
 )
+from policyengine_core.simulations.simulation import Simulation
 
 if TYPE_CHECKING:
     from policyengine_core.taxbenefitsystems.tax_benefit_system import (
         TaxBenefitSystem,
     )
 
-from policyengine_core.variables import Variable
 from datetime import datetime
 
+from policyengine_core.variables import Variable
+
 
 class SimulationBuilder:
     def __init__(self):
diff --git a/policyengine_core/simulations/simulation_macro_cache.py b/policyengine_core/simulations/simulation_macro_cache.py
index 80520c6b3..5c720e956 100644
--- a/policyengine_core/simulations/simulation_macro_cache.py
+++ b/policyengine_core/simulations/simulation_macro_cache.py
@@ -1,8 +1,9 @@
+import importlib.metadata
 import shutil
 from pathlib import Path
+
 import h5py
 from numpy.typing import ArrayLike
-import importlib.metadata
 
 from policyengine_core.taxbenefitsystems import TaxBenefitSystem
 
diff --git a/policyengine_core/taxbenefitsystems/tax_benefit_system.py b/policyengine_core/taxbenefitsystems/tax_benefit_system.py
index 077f6f27e..fc6539a81 100644
--- a/policyengine_core/taxbenefitsystems/tax_benefit_system.py
+++ b/policyengine_core/taxbenefitsystems/tax_benefit_system.py
@@ -6,13 +6,11 @@
 import inspect
 import logging
 import os
-import yaml
-from pathlib import Path
 import sys
 import traceback
 import typing
+from pathlib import Path
 from typing import (
-    TYPE_CHECKING,
     Any,
     Callable,
     Dict,
@@ -20,21 +18,20 @@
     Optional,
     Sequence,
     Type,
-    Union,
 )
-import importlib
+
+import yaml
 
 from policyengine_core import commons, periods, variables
-from policyengine_core.data_structures.reference import Reference
 from policyengine_core.entities import Entity
 from policyengine_core.errors import (
     VariableNameConflictError,
     VariableNotFoundError,
 )
 from policyengine_core.parameters import (
+    Parameter,
     ParameterNode,
     ParameterNodeAtInstant,
-    Parameter,
 )
 from policyengine_core.parameters.operations.homogenize_parameters import (
     homogenize_parameter_structures,
@@ -174,7 +171,7 @@ def add_abolition_parameters(self):
                     "unit": "bool",
                 },
             }
-        if not "abolitions" in self.parameters.gov.children:
+        if "abolitions" not in self.parameters.gov.children:
             self.parameters.gov.add_child(
                 "abolitions",
                 ParameterNode(name="gov.abolitions", data=abolition_folder_data),
diff --git a/policyengine_core/tools/google_cloud.py b/policyengine_core/tools/google_cloud.py
index 791b1121b..dc56864e4 100644
--- a/policyengine_core/tools/google_cloud.py
+++ b/policyengine_core/tools/google_cloud.py
@@ -60,8 +60,8 @@ def download_gcs_file(
         The local path where the file was saved.
     """
     try:
-        from google.cloud import storage
         import google.auth
+        from google.cloud import storage
     except ImportError:
         raise ImportError(
             "google-cloud-storage is required for gs:// URLs. "
@@ -103,8 +103,8 @@ def upload_gcs_file(
         version_metadata: Optional version string to store in blob metadata.
     """
     try:
-        from google.cloud import storage
         import google.auth
+        from google.cloud import storage
     except ImportError:
         raise ImportError(
             "google-cloud-storage is required for gs:// URLs. "
diff --git a/policyengine_core/tools/hugging_face.py b/policyengine_core/tools/hugging_face.py
index 7964658f3..ee008fb09 100644
--- a/policyengine_core/tools/hugging_face.py
+++ b/policyengine_core/tools/hugging_face.py
@@ -1,13 +1,14 @@
+import os
+import traceback
+import warnings
+from getpass import getpass
+
 from huggingface_hub import (
+    ModelInfo,
     hf_hub_download,
     model_info,
-    ModelInfo,
 )
 from huggingface_hub.errors import RepositoryNotFoundError
-from getpass import getpass
-import os
-import warnings
-import traceback
 
 with warnings.catch_warnings():
     warnings.simplefilter("ignore")
@@ -66,11 +67,11 @@ def download_huggingface_dataset(
     try:
         fetched_model_info: ModelInfo = model_info(repo)
         is_repo_private: bool = fetched_model_info.private
-    except RepositoryNotFoundError as e:
+    except RepositoryNotFoundError:
         # If this error type arises, it's likely the repo is private; see docs above
         is_repo_private = True
         pass
-    except Exception as e:
+    except Exception:
         # Otherwise, there probably is just a download error
         raise Exception(
             f"Unable to download dataset {repo_filename} from Hugging Face. This may be because the repo "
diff --git a/policyengine_core/tools/test_from_situation.py b/policyengine_core/tools/test_from_situation.py
index 4ec3bb862..4e6e43ca7 100644
--- a/policyengine_core/tools/test_from_situation.py
+++ b/policyengine_core/tools/test_from_situation.py
@@ -1,7 +1,6 @@
-import yaml
 from pathlib import Path
-import numpy as np
-import json
+
+import yaml
 
 
 def generate_test_from_situation(situation: dict, file_path: str):
diff --git a/policyengine_core/tools/test_runner.py b/policyengine_core/tools/test_runner.py
index 1874ceed7..1468b8b8a 100644
--- a/policyengine_core/tools/test_runner.py
+++ b/policyengine_core/tools/test_runner.py
@@ -1,28 +1,26 @@
 # -*- coding: utf-8 -*-
 
 import logging
-import sys
 import os
-import traceback
+import sys
 import textwrap
+import traceback
 from typing import Dict, List
 
 import pytest
 
 from policyengine_core.enums import EnumArray
-from policyengine_core.tools import (
-    assert_enum_equals,
-    assert_datetime_equals,
-    eval_expression,
-)
-from policyengine_core.simulations import SimulationBuilder
 from policyengine_core.errors import (
     SituationParsingError,
     VariableNotFoundError,
 )
-from policyengine_core.scripts import build_tax_benefit_system
 from policyengine_core.reforms import Reform, set_parameter
-from policyengine_core.populations import ADD, DIVIDE
+from policyengine_core.simulations import SimulationBuilder
+from policyengine_core.tools import (
+    assert_datetime_equals,
+    assert_enum_equals,
+    eval_expression,
+)
 
 log = logging.getLogger(__name__)
 
@@ -196,7 +194,7 @@ def runtest(self):
                         key,
                         value,
                         return_modifier=True,
-                        period=f"year:2000:40",
+                        period="year:2000:40",
                     )
                 ]
                 parametric_reform_items.append((key, value))
diff --git a/policyengine_core/tracers/__init__.py b/policyengine_core/tracers/__init__.py
index e6b07cbd5..d4bcf3da5 100644
--- a/policyengine_core/tracers/__init__.py
+++ b/policyengine_core/tracers/__init__.py
@@ -2,7 +2,7 @@
 from .flat_trace import FlatTrace
 from .full_tracer import FullTracer
 from .performance_log import PerformanceLog
-from .variable_graph import VariableGraph
 from .simple_tracer import SimpleTracer
 from .trace_node import TraceNode
 from .tracing_parameter_node_at_instant import TracingParameterNodeAtInstant
+from .variable_graph import VariableGraph
diff --git a/policyengine_core/tracers/trace_node.py b/policyengine_core/tracers/trace_node.py
index 501648774..4844caeb4 100644
--- a/policyengine_core/tracers/trace_node.py
+++ b/policyengine_core/tracers/trace_node.py
@@ -7,7 +7,6 @@
     import numpy
 
     from policyengine_core.enums import EnumArray
-    from policyengine_core.periods import Period
 
     Array = typing.Union[EnumArray, numpy.typing.ArrayLike]
     Time = typing.Union[float, int]
diff --git a/policyengine_core/tracers/tracing_parameter_node_at_instant.py b/policyengine_core/tracers/tracing_parameter_node_at_instant.py
index d4bf17466..eae2efde9 100644
--- a/policyengine_core/tracers/tracing_parameter_node_at_instant.py
+++ b/policyengine_core/tracers/tracing_parameter_node_at_instant.py
@@ -11,6 +11,7 @@
 
 if typing.TYPE_CHECKING:
     from numpy.typing import ArrayLike
+
     from policyengine_core.parameters import (
         ParameterNodeAtInstant,
         VectorialParameterNodeAtInstant,
diff --git a/policyengine_core/tracers/variable_graph.py b/policyengine_core/tracers/variable_graph.py
index 723e20e99..b29e2ed51 100644
--- a/policyengine_core/tracers/variable_graph.py
+++ b/policyengine_core/tracers/variable_graph.py
@@ -6,14 +6,12 @@
 from typing import Optional, Union
 
 import numpy
-from pyvis.node import Node
+from pyvis.network import Network
 
 from policyengine_core.enums import EnumArray
 
 from .. import tracers
 
-from pyvis.network import Network
-
 if typing.TYPE_CHECKING:
     from numpy.typing import ArrayLike
 
diff --git a/policyengine_core/types/data_types/arrays.py b/policyengine_core/types/data_types/arrays.py
index 4068906fb..120050ca6 100644
--- a/policyengine_core/types/data_types/arrays.py
+++ b/policyengine_core/types/data_types/arrays.py
@@ -1,5 +1,4 @@
-from typing import Sequence, TypeVar, Any
-from numpy.typing import NDArray as ArrayType
+from typing import Sequence, TypeVar
 
 T = TypeVar("T", bool, bytes, float, int, object, str)
 
diff --git a/policyengine_core/variables/defined_for.py b/policyengine_core/variables/defined_for.py
index 597bc874b..5f9dd35fb 100644
--- a/policyengine_core/variables/defined_for.py
+++ b/policyengine_core/variables/defined_for.py
@@ -2,10 +2,9 @@
 
 import numpy as np
 from numpy.typing import ArrayLike
-from policyengine_core.entities import Entity
-from policyengine_core.populations import GroupPopulation, Population
-from policyengine_core.projectors import EntityToPersonProjector, Projector
-from policyengine_core.variables import Variable
+
+from policyengine_core.populations import Population
+from policyengine_core.projectors import EntityToPersonProjector
 
 
 class CallableSubset:
diff --git a/policyengine_core/variables/variable.py b/policyengine_core/variables/variable.py
index dda76e0bb..5880d96cb 100644
--- a/policyengine_core/variables/variable.py
+++ b/policyengine_core/variables/variable.py
@@ -10,12 +10,11 @@
 from policyengine_core import periods, tools
 from policyengine_core.entities import Entity
 from policyengine_core.enums import Enum, EnumArray
-from policyengine_core.periods import Period
 from policyengine_core.holders import (
     set_input_dispatch_by_period,
     set_input_divide_by_period,
 )
-from policyengine_core.periods import DAY, ETERNITY
+from policyengine_core.periods import DAY, ETERNITY, Period
 
 from . import config, helpers
 
diff --git a/pyproject.toml b/pyproject.toml
index 85f789b15..6f30248f9 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -103,3 +103,19 @@ showcontent = true
 directory = "removed"
 name = "Removed"
 showcontent = true
+
+[tool.ruff.lint]
+select = ["E", "F", "I"]
+ignore = [
+    "E402",  # module-import-not-at-top-of-file
+    "E501",  # line too long (handled by ruff format)
+    "E712",  # true-false-comparison (common in numpy/pandas code)
+    "E721",  # type-comparison
+    "E722",  # bare-except
+    "E741",  # ambiguous-variable-name
+    "F401",  # unused-import (many are intentional re-exports)
+    "F403",  # undefined-local-with-import-star
+    "F405",  # undefined-local-with-import-star-usage
+    "F811",  # redefined-while-unused
+    "F841",  # unused-variable
+]
diff --git a/test.ipynb b/test.ipynb
index 310c0da93..6a29ad645 100644
--- a/test.ipynb
+++ b/test.ipynb
@@ -7,6 +7,7 @@
    "outputs": [],
    "source": [
     "from policyengine_uk import Microsimulation\n",
+    "\n",
     "from policyengine_core.reforms import Reform\n",
     "\n",
     "reform = Reform.from_dict(\n",
diff --git a/tests/core/commons/test_between_function.py b/tests/core/commons/test_between_function.py
index 7ad050567..aff5b033d 100644
--- a/tests/core/commons/test_between_function.py
+++ b/tests/core/commons/test_between_function.py
@@ -1,7 +1,7 @@
 """Test the between function from commons.formulas."""
 
 import numpy as np
-import pytest
+
 from policyengine_core.commons.formulas import between
 
 
diff --git a/tests/core/commons/test_is_in_function.py b/tests/core/commons/test_is_in_function.py
index ee724ffda..edd976b9e 100644
--- a/tests/core/commons/test_is_in_function.py
+++ b/tests/core/commons/test_is_in_function.py
@@ -1,7 +1,7 @@
 """Test the is_in function from commons.formulas."""
 
 import numpy as np
-import pytest
+
 from policyengine_core.commons.formulas import is_in
 
 
diff --git a/tests/core/commons/test_random_seed.py b/tests/core/commons/test_random_seed.py
index e63abe3f7..68cd73d36 100644
--- a/tests/core/commons/test_random_seed.py
+++ b/tests/core/commons/test_random_seed.py
@@ -1,8 +1,9 @@
 """Test the random function with large entity IDs to ensure no overflow."""
 
-import numpy as np
-import pytest
 from unittest.mock import Mock
+
+import numpy as np
+
 from policyengine_core.commons.formulas import random
 
 
diff --git a/tests/core/data/test_dataset.py b/tests/core/data/test_dataset.py
index d53703659..b74bdadec 100644
--- a/tests/core/data/test_dataset.py
+++ b/tests/core/data/test_dataset.py
@@ -1,11 +1,11 @@
-from pathlib import Path
-from tempfile import NamedTemporaryFile
 import sys
-import threading
-from policyengine_core.tools.win_file_manager import WindowsAtomicFileManager
 import tempfile
-from pathlib import Path
+import threading
 import uuid
+from pathlib import Path
+from tempfile import NamedTemporaryFile
+
+from policyengine_core.tools.win_file_manager import WindowsAtomicFileManager
 
 
 def test_dataset_class():
diff --git a/tests/core/enums/test_enum.py b/tests/core/enums/test_enum.py
index 19983f835..52811251b 100644
--- a/tests/core/enums/test_enum.py
+++ b/tests/core/enums/test_enum.py
@@ -1,5 +1,6 @@
-import pytest
 import numpy as np
+import pytest
+
 from policyengine_core.enums.enum import Enum
 from policyengine_core.enums.enum_array import EnumArray
 
diff --git a/tests/core/parameters/test_numpy2_structured_arrays.py b/tests/core/parameters/test_numpy2_structured_arrays.py
index b0a4be1be..97c4e2af2 100644
--- a/tests/core/parameters/test_numpy2_structured_arrays.py
+++ b/tests/core/parameters/test_numpy2_structured_arrays.py
@@ -10,7 +10,7 @@
 
 import numpy as np
 import pytest
-from policyengine_core.parameters import ParameterNode
+
 from policyengine_core.parameters.vectorial_parameter_node_at_instant import (
     VectorialParameterNodeAtInstant,
 )
diff --git a/tests/core/parameters_fancy_indexing/test_fancy_indexing.py b/tests/core/parameters_fancy_indexing/test_fancy_indexing.py
index a3eaed648..1b9b53f4f 100644
--- a/tests/core/parameters_fancy_indexing/test_fancy_indexing.py
+++ b/tests/core/parameters_fancy_indexing/test_fancy_indexing.py
@@ -1,14 +1,12 @@
 # -*- coding: utf-8 -*-
 
 import os
-import re
 
 import numpy as np
 import pytest
 
 from policyengine_core.model_api import *
 from policyengine_core.parameters import (
-    Parameter,
     ParameterNode,
     ParameterNotFoundError,
 )
diff --git a/tests/core/test_countries.py b/tests/core/test_countries.py
index 6fa70b457..d1d2ce449 100644
--- a/tests/core/test_countries.py
+++ b/tests/core/test_countries.py
@@ -3,9 +3,7 @@
 from policyengine_core import periods, populations, tools
 from policyengine_core.errors import (
     VariableNameConflictError,
-    VariableNotFoundError,
 )
-from policyengine_core.simulations import SimulationBuilder
 from policyengine_core.variables import Variable
 
 PERIOD = periods.period("2016-01")
diff --git a/tests/core/test_cycles.py b/tests/core/test_cycles.py
index a488765b1..318a081be 100644
--- a/tests/core/test_cycles.py
+++ b/tests/core/test_cycles.py
@@ -3,7 +3,7 @@
 from policyengine_core import periods, tools
 from policyengine_core.country_template import entities
 from policyengine_core.errors import CycleError
-from policyengine_core.simulations import SimulationBuilder, Simulation
+from policyengine_core.simulations import Simulation, SimulationBuilder
 from policyengine_core.variables import Variable
 
 
diff --git a/tests/core/test_entities.py b/tests/core/test_entities.py
index f9660e112..e11feccf6 100644
--- a/tests/core/test_entities.py
+++ b/tests/core/test_entities.py
@@ -1,5 +1,5 @@
 from copy import deepcopy
-from typing import Dict, Any
+from typing import Any, Dict
 
 from policyengine_core import tools
 from policyengine_core.country_template import entities, situation_examples
diff --git a/tests/core/test_holders.py b/tests/core/test_holders.py
index 94aebe09d..70c3b2858 100644
--- a/tests/core/test_holders.py
+++ b/tests/core/test_holders.py
@@ -4,7 +4,6 @@
 from policyengine_core import holders, periods, tools
 from policyengine_core.country_template import situation_examples
 from policyengine_core.country_template.variables import housing
-from policyengine_core.errors import PeriodMismatchError
 from policyengine_core.experimental import MemoryConfig
 from policyengine_core.holders import Holder
 from policyengine_core.simulations import SimulationBuilder
diff --git a/tests/core/test_microsimulation_person_accessor.py b/tests/core/test_microsimulation_person_accessor.py
index 0f9cebd64..7ba3cfff0 100644
--- a/tests/core/test_microsimulation_person_accessor.py
+++ b/tests/core/test_microsimulation_person_accessor.py
@@ -11,7 +11,6 @@
 """
 
 import numpy as np
-import pytest
 from microdf import MicroSeries
 
 from policyengine_core.country_template import Microsimulation
diff --git a/tests/core/test_pandas3_compatibility.py b/tests/core/test_pandas3_compatibility.py
index 8687bf225..a0a128288 100644
--- a/tests/core/test_pandas3_compatibility.py
+++ b/tests/core/test_pandas3_compatibility.py
@@ -20,8 +20,8 @@ def test_filled_array_with_string_dtype(self):
         In pandas 3.0.0, string columns use StringDtype by default.
         numpy.full() cannot handle StringDtype, so we need to handle this case.
         """
-        from policyengine_core.populations.population import Population
         from policyengine_core.entities import Entity
+        from policyengine_core.populations.population import Population
 
         # Create a minimal entity for testing
         entity = Entity(
@@ -53,8 +53,8 @@ def test_filled_array_with_pyarrow_string_dtype(self):
         """
         pa = pytest.importorskip("pyarrow")
 
-        from policyengine_core.populations.population import Population
         from policyengine_core.entities import Entity
+        from policyengine_core.populations.population import Population
 
         entity = Entity(
             key="person",
@@ -101,11 +101,13 @@ def test_parameter_node_at_instant_getitem_with_string_array(self):
 
         This is issue #429.
         """
-        from policyengine_core.parameters import ParameterNode
-        import tempfile
         import os
+        import tempfile
+
         import yaml
 
+        from policyengine_core.parameters import ParameterNode
+
         # Create a minimal parameter tree for testing
         with tempfile.TemporaryDirectory() as tmpdir:
             # Create parameter YAML files
diff --git a/tests/core/test_projectors.py b/tests/core/test_projectors.py
index b1795336e..b52decdd5 100644
--- a/tests/core/test_projectors.py
+++ b/tests/core/test_projectors.py
@@ -4,7 +4,6 @@
 from policyengine_core.entities import build_entity
 from policyengine_core.model_api import ETERNITY, Enum, Variable
 from policyengine_core.simulations.simulation_builder import SimulationBuilder
-
 from policyengine_core.taxbenefitsystems import TaxBenefitSystem
 
 
diff --git a/tests/core/test_reforms.py b/tests/core/test_reforms.py
index a6075ed9d..55611a54f 100644
--- a/tests/core/test_reforms.py
+++ b/tests/core/test_reforms.py
@@ -2,7 +2,6 @@
 
 import pytest
 
-from policyengine_core import periods
 from policyengine_core.country_template.entities import Household, Person
 from policyengine_core.model_api import *
 from policyengine_core.parameters import ParameterNode
diff --git a/tests/core/test_simulations.py b/tests/core/test_simulations.py
index c6cf3140c..00ee7e2df 100644
--- a/tests/core/test_simulations.py
+++ b/tests/core/test_simulations.py
@@ -1,11 +1,13 @@
+import importlib.metadata
+from pathlib import Path
+
+import numpy as np
+
 from policyengine_core.country_template.situation_examples import single
 from policyengine_core.simulations import SimulationBuilder
 from policyengine_core.simulations.simulation_macro_cache import (
     SimulationMacroCache,
 )
-import importlib.metadata
-import numpy as np
-from pathlib import Path
 
 
 def test_calculate_full_tracer(tax_benefit_system):
diff --git a/tests/core/test_tracers.py b/tests/core/test_tracers.py
index e653f39be..2a9a818d5 100644
--- a/tests/core/test_tracers.py
+++ b/tests/core/test_tracers.py
@@ -1,8 +1,6 @@
 # -*- coding: utf-8 -*-
 
-import csv
 import json
-import os
 
 import numpy as np
 from pytest import approx, fixture, mark, raises
diff --git a/tests/core/tools/test_google_cloud.py b/tests/core/tools/test_google_cloud.py
index ccb0403ba..0ec1e2a41 100644
--- a/tests/core/tools/test_google_cloud.py
+++ b/tests/core/tools/test_google_cloud.py
@@ -1,4 +1,5 @@
 import pytest
+
 from policyengine_core.tools.google_cloud import parse_gs_url
 
 
diff --git a/tests/core/tools/test_hugging_face.py b/tests/core/tools/test_hugging_face.py
index 2a68682e2..52d508c46 100644
--- a/tests/core/tools/test_hugging_face.py
+++ b/tests/core/tools/test_hugging_face.py
@@ -1,11 +1,13 @@
 import os
+from unittest.mock import MagicMock, patch
+
 import pytest
-from unittest.mock import patch, MagicMock
 from huggingface_hub import ModelInfo
 from huggingface_hub.errors import RepositoryNotFoundError
+
 from policyengine_core.tools.hugging_face import (
-    get_or_prompt_hf_token,
     download_huggingface_dataset,
+    get_or_prompt_hf_token,
     parse_hf_url,
 )
 
diff --git a/tests/core/tools/test_runner/test_yaml_runner.py b/tests/core/tools/test_runner/test_yaml_runner.py
index 72e3faadb..3443e8501 100644
--- a/tests/core/tools/test_runner/test_yaml_runner.py
+++ b/tests/core/tools/test_runner/test_yaml_runner.py
@@ -1,9 +1,9 @@
 import os
+from pathlib import Path
 from typing import List
 
 import numpy as np
 import pytest
-from pathlib import Path
 
 from policyengine_core.entities import Entity
 from policyengine_core.errors import VariableNotFoundError
diff --git a/tests/core/variables/test_adds.py b/tests/core/variables/test_adds.py
index ff6f5bdd9..01f00ca74 100644
--- a/tests/core/variables/test_adds.py
+++ b/tests/core/variables/test_adds.py
@@ -1,5 +1,3 @@
-import numpy as np
-
 from policyengine_core.entities import Entity
 from policyengine_core.model_api import *
 from policyengine_core.simulations import SimulationBuilder
@@ -32,5 +30,5 @@ class some_income(Variable):
     try:
         simulation.calculate("some_income")
         raise Exception("Should have raised an error.")
-    except ValueError as e:
+    except ValueError:
         pass
diff --git a/tests/core/variables/test_bounds.py b/tests/core/variables/test_bounds.py
index b76285b69..912369c6b 100644
--- a/tests/core/variables/test_bounds.py
+++ b/tests/core/variables/test_bounds.py
@@ -1,8 +1,9 @@
+from test_variables import get_message
+
 import policyengine_core.country_template as country_template
 from policyengine_core.country_template.entities import Person
-from policyengine_core.variables import Variable
 from policyengine_core.periods import YEAR
-from test_variables import get_message
+from policyengine_core.variables import Variable
 
 tax_benefit_system = country_template.CountryTaxBenefitSystem()
 
diff --git a/tests/core/variables/test_subtracts.py b/tests/core/variables/test_subtracts.py
index eeba872fa..822d6055f 100644
--- a/tests/core/variables/test_subtracts.py
+++ b/tests/core/variables/test_subtracts.py
@@ -1,5 +1,3 @@
-import numpy as np
-
 from policyengine_core.entities import Entity
 from policyengine_core.model_api import *
 from policyengine_core.simulations import SimulationBuilder
@@ -32,5 +30,5 @@ class some_income(Variable):
     try:
         simulation.calculate("some_income")
         raise Exception("Should have raised an error.")
-    except ValueError as e:
+    except ValueError:
         pass
diff --git a/tests/fixtures/variables.py b/tests/fixtures/variables.py
index 600107515..b99417e5b 100644
--- a/tests/fixtures/variables.py
+++ b/tests/fixtures/variables.py
@@ -1,5 +1,4 @@
 from policyengine_core import periods
-from policyengine_core.entities import Entity
 from policyengine_core.variables import Variable
 
 
diff --git a/tests/smoke/test_us.py b/tests/smoke/test_us.py
index 65d328681..f8a92fcbb 100644
--- a/tests/smoke/test_us.py
+++ b/tests/smoke/test_us.py
@@ -1,4 +1,5 @@
 import os
+
 import pytest