diff --git a/capsul/application.py b/capsul/application.py
index 08df5aaa..3f9f0c66 100644
--- a/capsul/application.py
+++ b/capsul/application.py
@@ -33,7 +33,7 @@ def _is_nipype_interface(obj):
     if "nipype.interfaces.base" not in sys.modules:
         return False
     npype_base = sys.modules["nipype.interfaces.base"]
-    NipypeInterface = getattr(npype_base, "Interface")
+    NipypeInterface = npype_base.Interface
     return isinstance(obj, NipypeInterface)
 
 
@@ -48,7 +48,7 @@ def _is_nipype_interface_subclass(obj):
     if "nipype.interfaces.base" not in sys.modules:
         return False
     npype_base = sys.modules["nipype.interfaces.base"]
-    NipypeInterface = getattr(npype_base, "Interface")
+    NipypeInterface = npype_base.Interface
     return issubclass(obj, NipypeInterface)
 
 
@@ -258,7 +258,7 @@ def executable(definition, **kwargs):
             raise TypeError(
                 f"Class {definition} cannot be used to create a Process "
                 "because its module cannot be imported : {e}"
-            )
+            ) from e
         cls = getattr(module, object_name, None)
         if cls is not definition:
             raise TypeError(
@@ -503,8 +503,7 @@ def wrap(self, context):
             for i in annotations
             if i != "result" and getattr(self, i, undefined) is not undefined
         }
-        result = function(**kwargs)
-        setattr(self, "result", result)
+        self.result = function(**kwargs)
 
     namespace = {
         "__annotations__": annotations,
@@ -635,7 +634,7 @@ def _get_interface_class():
         if nipype is None:
             _interface = type("Interface", (object,), {})
         else:
-            _interface = getattr(nipype, "Interface")
+            _interface = nipype.Interface
             _nipype_loaded = True
     return _interface
 
diff --git a/capsul/config/configuration.py b/capsul/config/configuration.py
index 8336a320..d65f352f 100644
--- a/capsul/config/configuration.py
+++ b/capsul/config/configuration.py
@@ -195,8 +195,7 @@ def add_module(self, module_name, allow_existing=False):
         self.config_modules.append(module_name)
 
         if hasattr(cls, "module_dependencies"):
-            module_dependencies = getattr(cls, "module_dependencies")
-            for dependency in module_dependencies:
+            for dependency in cls.module_dependencies:
                 self.add_module(dependency, allow_existing=True)
 
     def remove_module(self, module_name):
@@ -506,9 +505,9 @@ def merge_configs(self):
     def available_modules():
         module = sys.modules.get(__name__)
         mod_base = module.__name__.rsplit(".", 1)[0]
-        mod_path = getattr(module, "__file__")
+        mod_path = module.__file__
         if mod_path is None:
-            mod_path = getattr(module, "__path__")
+            mod_path = module.__path__
         mod_dir = os.path.dirname(mod_path)
         modules = []
         for p in os.listdir(mod_dir):
diff --git a/capsul/engine/__init__.py b/capsul/engine/__init__.py
index 444583b8..46add13e 100644
--- a/capsul/engine/__init__.py
+++ b/capsul/engine/__init__.py
@@ -170,7 +170,7 @@ def engine_status(self):
                 if engine_id:
                     result["workers_count"] = database.workers_count(engine_id)
                     result["connections"] = database.engine_connections(engine_id)
-                    result["persistent"]: database.persistent(engine_id)
+                    result["persistent"] = database.persistent(engine_id)
         return result
 
     def start_workers(self):
diff --git a/capsul/execution_context.py b/capsul/execution_context.py
index 2206ffd9..fe34824a 100644
--- a/capsul/execution_context.py
+++ b/capsul/execution_context.py
@@ -772,15 +772,15 @@ def find_temporary_to_generate(executable):
         field.generate_temporary = False
         if isinstance(node, ProcessIteration):
             node.process.field(field.name).generate_temporary = field.generate_temporary
-        for node, parameter in executable.get_linked_items(
+        for snode, parameter in executable.get_linked_items(
             node, field.name, direction="links_from", in_outer_pipelines=True
         ):
             if isinstance(node, ProcessIteration):
-                stack.append((node.process, node.process.field(parameter)))
-                # print('!temporaries!   + ', node.process.full_name, ':', parameter)
+                stack.append((snode.process, snode.process.field(parameter)))
+                # print('!temporaries!   + ', snode.process.full_name, ':', parameter)
             else:
-                stack.append((node, node.field(parameter)))
-                # print('!temporaries!   + ', node.full_name, ':', parameter)
+                stack.append((snode, snode.field(parameter)))
+                # print('!temporaries!   + ', snode.full_name, ':', parameter)
 
     # print('!temporaries!  parameters with temporary')
     # for n, p in temporaries:
diff --git a/capsul/pipeline/custom_nodes/cv_node.py b/capsul/pipeline/custom_nodes/cv_node.py
index b0562805..9af9a17a 100644
--- a/capsul/pipeline/custom_nodes/cv_node.py
+++ b/capsul/pipeline/custom_nodes/cv_node.py
@@ -82,8 +82,8 @@ def params_to_command(self):
     def build_job(
         self,
         name=None,
-        referenced_input_files=[],
-        referenced_output_files=[],
+        referenced_input_files=None,
+        referenced_output_files=None,
         param_dict=None,
     ):
         from soma_workflow.custom_jobs import CrossValidationFoldJob
@@ -97,6 +97,8 @@ def build_job(
         param_dict["test"] = self.test
         param_dict["nfolds"] = self.nfolds
         param_dict["fold"] = self.fold
+        referenced_input_files = referenced_input_files or []
+        referenced_output_files = referenced_input_files or []
         job = CrossValidationFoldJob(
             name=name,
             referenced_input_files=referenced_input_files,
diff --git a/capsul/pipeline/custom_nodes/loo_node.py b/capsul/pipeline/custom_nodes/loo_node.py
index a4d22b07..f1534cd8 100644
--- a/capsul/pipeline/custom_nodes/loo_node.py
+++ b/capsul/pipeline/custom_nodes/loo_node.py
@@ -118,8 +118,8 @@ def params_to_command(self):
     def build_job(
         self,
         name=None,
-        referenced_input_files=[],
-        referenced_output_files=[],
+        referenced_input_files=None,
+        referenced_output_files=None,
         param_dict=None,
     ):
         from soma_workflow.custom_jobs import LeaveOneOutJob
@@ -134,6 +134,8 @@ def build_job(
                 pass
         param_dict = dict(param_dict)
         param_dict["index"] = index
+        referenced_input_files = referenced_input_files or []
+        referenced_output_files = referenced_output_files or []
         job = LeaveOneOutJob(
             name=name,
             referenced_input_files=referenced_input_files,
diff --git a/capsul/pipeline/custom_nodes/map_node.py b/capsul/pipeline/custom_nodes/map_node.py
index 2517772d..1db56b5c 100644
--- a/capsul/pipeline/custom_nodes/map_node.py
+++ b/capsul/pipeline/custom_nodes/map_node.py
@@ -38,10 +38,12 @@ def __init__(
         self,
         pipeline,
         name,
-        input_names=["inputs"],
-        output_names=["output_%d"],
+        input_names=None,
+        output_names=None,
         input_types=None,
     ):
+        input_names = input_names or ["inputs"]
+        output_names = output_names or ["output_%d"]
         in_fields = []
         out_fields = [{"name": "lengths", "optional": True}]
 
@@ -153,8 +155,8 @@ def params_to_command(self):
     def build_job(
         self,
         name=None,
-        referenced_input_files=[],
-        referenced_output_files=[],
+        referenced_input_files=None,
+        referenced_output_files=None,
         param_dict=None,
     ):
         from soma_workflow.custom_jobs import MapJob
@@ -170,6 +172,8 @@ def build_job(
                 for i in range(len(value)):
                     opname = output_name % i
                     param_dict[opname] = getattr(self, opname)
+        referenced_input_files = referenced_input_files or []
+        referenced_output_files = referenced_output_files or []
         job = MapJob(
             name=name,
             referenced_input_files=referenced_input_files,
diff --git a/capsul/pipeline/custom_nodes/reduce_node.py b/capsul/pipeline/custom_nodes/reduce_node.py
index 7ddfdbde..f403c915 100644
--- a/capsul/pipeline/custom_nodes/reduce_node.py
+++ b/capsul/pipeline/custom_nodes/reduce_node.py
@@ -34,10 +34,12 @@ def __init__(
         self,
         pipeline,
         name,
-        input_names=["input_%d"],
-        output_names=["outputs"],
+        input_names=None,
+        output_names=None,
         input_types=None,
     ):
+        input_names = input_names or ["input_%d"]
+        output_names = output_names or ["outputs"]
         in_fields = [
             {"name": "lengths", "optional": True},
             {"name": "skip_empty", "optional": True},
@@ -209,8 +211,8 @@ def params_to_command(self):
     def build_job(
         self,
         name=None,
-        referenced_input_files=[],
-        referenced_output_files=[],
+        referenced_input_files=None,
+        referenced_output_files=None,
         param_dict=None,
     ):
         from soma_workflow.custom_jobs import MapJob
@@ -227,6 +229,8 @@ def build_job(
             value = getattr(self, output_name, undefined)
             if value not in (None, undefined):
                 param_dict[output_name] = value
+        referenced_input_files = referenced_input_files or []
+        referenced_output_files = referenced_output_files or []
         job = MapJob(
             name=name,
             referenced_input_files=referenced_input_files,
diff --git a/capsul/pipeline/custom_nodes/strcat_node.py b/capsul/pipeline/custom_nodes/strcat_node.py
index 34149b57..807b3f4d 100644
--- a/capsul/pipeline/custom_nodes/strcat_node.py
+++ b/capsul/pipeline/custom_nodes/strcat_node.py
@@ -24,7 +24,7 @@ def __init__(
         concat_plug,
         outputs,
         make_optional=(),
-        param_types={},
+        param_types=None,
     ):
         """
         Parameters
@@ -46,6 +46,7 @@ def __init__(
             parameters types dict: {param_name: field_type_as_string}
 
         """
+        param_types = param_types or {}
         node_inputs = [
             dict(name=i, optional=(i in make_optional))
             for i in params
@@ -69,7 +70,8 @@ def __init__(
         self.cat_callback()
         self.set_callbacks()
 
-    def add_parameters(self, param_types={}):
+    def add_parameters(self, param_types=None):
+        param_types = param_types or {}
         added_fields = [self._concat_plug]
         for name in self._concat_sequence + added_fields:
             plug = self.plugs[name]
@@ -133,8 +135,8 @@ def params_to_command(self):
     def build_job(
         self,
         name=None,
-        referenced_input_files=[],
-        referenced_output_files=[],
+        referenced_input_files=None,
+        referenced_output_files=None,
         param_dict=None,
     ):
         from soma_workflow.custom_jobs import StrCatJob
@@ -147,6 +149,8 @@ def build_job(
         # [re] build the concatenated output
         self.cat_callback()
         param_dict[self._concat_plug] = getattr(self, self._concat_plug)
+        referenced_input_files = referenced_input_files or []
+        referenced_output_files = referenced_output_files or []
         job = StrCatJob(
             name=name,
             referenced_input_files=referenced_input_files,
diff --git a/capsul/pipeline/pipeline.py b/capsul/pipeline/pipeline.py
index 117b676a..d2fd5190 100644
--- a/capsul/pipeline/pipeline.py
+++ b/capsul/pipeline/pipeline.py
@@ -2460,10 +2460,10 @@ def __setitem__(self, path, value):
     def dispatch_value(self, node, name, value):
         """Propagate the value from a pipeline plug through links"""
         # print(f"!dispatch! {node.name}.{name} = {value}")
-        for node, plug in self.dispatch_plugs(node, name):
-            # print(f"!dispatch! -> {node.name}.{plug}")
-            if getattr(node, plug, undefined) != value:
-                setattr(node, plug, value)
+        for snode, plug in self.dispatch_plugs(node, name):
+            # print(f"!dispatch! -> {snode.name}.{plug}")
+            if getattr(snode, plug, undefined) != value:
+                setattr(snode, plug, value)
 
     def dispatch_plugs(self, node, name):
         """generator through linked plugs"""
@@ -2669,7 +2669,8 @@ def node_from_path(self, path):
 
 
 class CustomPipeline(Pipeline):
-    def __init__(self, definition="custom_pipeline", json_executable={}):
+    def __init__(self, definition="custom_pipeline", json_executable=None):
+        json_executable = json_executable or {}
         object.__setattr__(self, "json_executable", json_executable)
         super().__init__(
             definition=definition,
diff --git a/capsul/pipeline/pipeline_tools.py b/capsul/pipeline/pipeline_tools.py
index f6ebeae8..af248c71 100644
--- a/capsul/pipeline/pipeline_tools.py
+++ b/capsul/pipeline/pipeline_tools.py
@@ -267,7 +267,7 @@ def pipeline_link_color(plug, link):
 
 
 def dot_graph_from_pipeline(
-    pipeline, nodes_sizes={}, use_nodes_pos=False, include_io=True, enlarge_boxes=0.0
+    pipeline, nodes_sizes=None, use_nodes_pos=False, include_io=True, enlarge_boxes=0.0
 ):
     """
     Build a graphviz/dot-compatible representation of the pipeline.
@@ -319,6 +319,7 @@ def _link_color(plug, link):
         active = plug.activated and link[3].activated
         return (0, 0, 0), style, active, link[4]
 
+    nodes_sizes = nodes_sizes or {}
     nodes = []
     edges = {}
     has_outputs = False
@@ -408,7 +409,7 @@ def _link_color(plug, link):
 
 
 def dot_graph_from_workflow(
-    pipeline, nodes_sizes={}, use_nodes_pos=False, enlarge_boxes=0.0
+    pipeline, nodes_sizes=None, use_nodes_pos=False, enlarge_boxes=0.0
 ):
     """
     Build a graphviz/dot-compatible representation of the pipeline workflow.
@@ -444,6 +445,7 @@ def dot_graph_from_workflow(
         :py:func:`save_dot_graph`
     """
 
+    nodes_sizes = nodes_sizes or {}
     graph = pipeline.workflow_graph()
     nodes = []
     edges = {}
@@ -536,7 +538,7 @@ def _str_repr(item):
 def save_dot_image(
     pipeline,
     filename,
-    nodes_sizes={},
+    nodes_sizes=None,
     use_nodes_pos=False,
     include_io=True,
     enlarge_boxes=0.0,
@@ -585,6 +587,7 @@ def save_dot_image(
     **kwargs: additional attributes for the dot graph
       like nodesep=0.1 or rankdir="TB"
     """
+    nodes_sizes = nodes_sizes or {}
     if workflow:
         dgraph = dot_graph_from_workflow(
             pipeline,
@@ -1382,7 +1385,7 @@ def __init__(self, value):
                         self.value = value
 
                     def __repr__(self):
-                        return "lambda: %s" % repr(value)
+                        return "lambda: %s" % repr(self.value)
 
                 meta["default_factory"] = def_fac(field.default_factory())
                 has_default = True
diff --git a/capsul/pipeline/python_export.py b/capsul/pipeline/python_export.py
index b1f2220d..f35dac55 100644
--- a/capsul/pipeline/python_export.py
+++ b/capsul/pipeline/python_export.py
@@ -139,7 +139,7 @@ def _write_process(process, pyf, name, enabled, skip_invalid):
 
             if isinstance(snode, Pipeline):
                 sself_str = '%s.nodes["%s"]' % (self_str, "%s")
-                for node_name, snode in snode.nodes.items():
+                for node_name, _ in snode.nodes.items():
                     scnode = cnode.nodes[node_name]
 
                     if node_name == "":
diff --git a/capsul/pipeline/test/test_activation.py b/capsul/pipeline/test/test_activation.py
index c89eead2..dca53cc7 100644
--- a/capsul/pipeline/test/test_activation.py
+++ b/capsul/pipeline/test/test_activation.py
@@ -131,7 +131,7 @@ def run_unactivation_tests_2(self):
         if not app:
             app = QtGui.QApplication(sys.argv)
         pipeline = executable(MyPipeline)
-        setattr(pipeline.nodes_activation, "way11", False)
+        pipeline.nodes_activation.way11 = False
         view1 = PipelineDeveloperView(pipeline)
         view1.show()
         app.exec_()
diff --git a/capsul/pipeline/test/test_complex_pipeline_activations.py b/capsul/pipeline/test/test_complex_pipeline_activations.py
index c0d63471..09cc31f4 100644
--- a/capsul/pipeline/test/test_complex_pipeline_activations.py
+++ b/capsul/pipeline/test/test_complex_pipeline_activations.py
@@ -857,10 +857,10 @@ def test_complex_activations(self):
             node_name = split[-1]
             try:
                 node = node_pipeline.nodes[node_name]
-            except KeyError:
+            except KeyError as e:
                 raise KeyError(
                     f"Pipeline {node_pipeline.pipeline} has no node named {node_name}"
-                )
+                ) from e
             try:
                 what = "activation of node {0}".format(
                     full_node_name or "main pipeline node"
@@ -876,10 +876,10 @@ def test_complex_activations(self):
                 if expected is not None:
                     got = node.enabled
                     self.assertEqual(expected, got)
-            except AssertionError:
+            except AssertionError as e:
                 raise AssertionError(
                     f"Wrong activation within ComplexPipeline with parameters {kwargs}: {what} is supposed to be {expected} but is {got}"
-                )
+                ) from e
 
 
 if __name__ == "__main__":
diff --git a/capsul/pipeline/test/test_pipeline.py b/capsul/pipeline/test/test_pipeline.py
index 866ea798..559d24ec 100644
--- a/capsul/pipeline/test/test_pipeline.py
+++ b/capsul/pipeline/test/test_pipeline.py
@@ -123,7 +123,7 @@ def test_enabled(self):
         self.assertEqual(workflow_repr, "")
 
     def test_run_pipeline(self):
-        setattr(self.pipeline.nodes_activation, "node2", True)
+        self.pipeline.nodes_activation.node2 = True
         tmp = tempfile.mkstemp("", prefix="capsul_test_pipeline")
         self.temp_files.append(tmp[1])
         ofile = tmp[1]
@@ -220,7 +220,7 @@ def test_pipeline_json(self):
         app = Qt.QApplication(sys.argv)
 
     pipeline = executable(MyPipeline)
-    setattr(pipeline.nodes_activation, "node2", True)
+    pipeline.nodes_activation.node2 = True
     view1 = PipelineDeveloperView(pipeline, allow_open_controller=True)
     view1.show()
     app.exec_()
diff --git a/capsul/pipeline/test/test_pipeline_parameters.py b/capsul/pipeline/test/test_pipeline_parameters.py
index bab34884..49fbcd92 100644
--- a/capsul/pipeline/test/test_pipeline_parameters.py
+++ b/capsul/pipeline/test/test_pipeline_parameters.py
@@ -738,7 +738,7 @@ def create_pipeline():
 
         with self.capsul.engine() as ce:
             ce.run(pipeline1, timeout=5)
-        pipeline1.out
+        assert pipeline1.out
 
         save_pipeline_parameters(self.path, pipeline1)
 
diff --git a/capsul/process/node.py b/capsul/process/node.py
index 56e0029a..e8fd991e 100644
--- a/capsul/process/node.py
+++ b/capsul/process/node.py
@@ -146,7 +146,7 @@ class Node(Controller):
     )
 
     def __init__(
-        self, definition=None, pipeline=None, name=None, inputs={}, outputs={}
+        self, definition=None, pipeline=None, name=None, inputs=None, outputs=None
     ):
         """Generate a Node
 
@@ -174,7 +174,7 @@ def __init__(
             the pipeline object where the node is added
         name: str
             the node name
-        inputs: list of dict
+        inputs: dict
             a list of input parameters containing a dictionary with default
             values (mandatory key: name)
         outputs: dict
@@ -224,6 +224,7 @@ def __init__(
         # generate a list with all the inputs and outputs
         # the second parameter (parameter_type) is False for an input,
         # True for an output
+        inputs = inputs or {}
         parameters = list(
             zip(
                 inputs,
@@ -233,6 +234,7 @@ def __init__(
                 * len(inputs),
             )
         )
+        outputs = outputs or {}
         parameters.extend(
             list(
                 zip(
diff --git a/capsul/process/process.py b/capsul/process/process.py
index c17fe04b..d46b1dbb 100644
--- a/capsul/process/process.py
+++ b/capsul/process/process.py
@@ -663,7 +663,8 @@ def _move_outputs(self):
         del self._former_output_directory
         return output_values
 
-    def _move_files(self, src_directory, dst_directory, value, moved_dict={}):
+    def _move_files(self, src_directory, dst_directory, value, moved_dict=None):
+        moved_dict = moved_dict or {}
         if isinstance(value, (list, tuple)):
             new_value = [
                 self._move_files(src_directory, dst_directory, item, moved_dict)
@@ -1109,7 +1110,7 @@ class Smooth(NipypeProcess):
         self.synchronize = sc.Event()
 
         # use the nipype doc for help
-        doc = getattr(nipype_instance, "__doc__")
+        doc = nipype_instance.__doc__
         if doc:
             self.__doc__ = doc
 
diff --git a/capsul/qt_gui/widgets/pipeline_developer_view.py b/capsul/qt_gui/widgets/pipeline_developer_view.py
index 5168b6e7..2dd442de 100644
--- a/capsul/qt_gui/widgets/pipeline_developer_view.py
+++ b/capsul/qt_gui/widgets/pipeline_developer_view.py
@@ -253,7 +253,7 @@ def __init__(
         sub_pipeline=None,
         colored_parameters=True,
         logical_view=False,
-        labels=[],
+        labels=None,
         show_opt_inputs=True,
         show_opt_outputs=True,
         userlevel=0,
@@ -283,7 +283,7 @@ def __init__(
                 if getattr(field, "hidden", False):
                     show = False
                 elif getattr(field, "userlevel", None) is not None:
-                    if getattr(field, "userlevel") > self.userlevel:
+                    if field.userlevel > self.userlevel:
                         show = False
             if show:
                 self.parameters[pname] = param
@@ -305,7 +305,7 @@ def __init__(
         self.show_opt_outputs = show_opt_outputs
 
         self.labels = []
-        self.scene_labels = labels
+        self.scene_labels = labels or []
         self.label_items = []
         my_labels = []
         steps = getattr(pipeline, "pipeline_steps", None)
@@ -392,7 +392,7 @@ def update_parameters_now(self):
             if getattr(param, "hidden", False):
                 show = False
             elif getattr(param, "userlevel", None) is not None:
-                if getattr(param, "userlevel") > self.userlevel:
+                if param.userlevel > self.userlevel:
                     show = False
             if show:
                 self.parameters[pname] = self.process.plugs[pname]
@@ -1848,7 +1848,7 @@ def _remove_link(self, source_dest):
             self.removeItem(glink)
             del self.glinks[new_source_dest]
 
-    def update_paths(self, regions=[]):
+    def update_paths(self, regions=None):
         for name, i in self.gnodes.items():
             self.pos[i.name] = i.pos()
             br = i.box.boundingRect()
@@ -3950,7 +3950,7 @@ def reset_initial_nodes_positions(self):
         #                     gnode.update(0,0,*dimension)
         #         #####################################################
 
-        pos = getattr(scene.pipeline, "node_position")
+        pos = scene.pipeline.node_position
         if pos is not None:
             scene.pos = pos
             for node, position in pos.items():
@@ -4820,7 +4820,7 @@ def show_node_doc(self, node):
                     doc_path = "file://%s" % os.path.abspath(doc_path)
                 doc_browser.setUrl(Qt.QUrl(doc_path))
             else:
-                gethelp = getattr(node, "get_help")
+                gethelp = node.get_help
                 msg = None
                 if gethelp:
                     msg = node.get_help(returnhelp=True)
diff --git a/capsul/test/test_capsul_notebooks.py b/capsul/test/test_capsul_notebooks.py
index d61e0678..21e98976 100644
--- a/capsul/test/test_capsul_notebooks.py
+++ b/capsul/test/test_capsul_notebooks.py
@@ -8,10 +8,10 @@
 try:
     import nbformat
     from jupyter_core.command import main as main_jupyter
-except ImportError:
+except ImportError as e:
     raise ImportError(
         "cannot import nbformat and/or jupyter_core.command: " "cannot test notebooks"
-    )
+    ) from e
 
 from soma.test_utils import test_notebook as tnb
 
diff --git a/doc/source/conf.py b/doc/source/conf.py
index df659dc6..89349098 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -19,8 +19,8 @@
 # Doc generation depends on being able to import capsul
 try:
     import capsul
-except ImportError:
-    raise RuntimeError("Cannot import CAPSUL, please investigate")
+except ImportError as e:
+    raise RuntimeError("Cannot import CAPSUL, please investigate") from e
 
 from distutils.version import LooseVersion