diff --git a/demo/plotEDFFile.py b/demo/plotEDFFile.py
index 7cfae39..2cc06db 100644
--- a/demo/plotEDFFile.py
+++ b/demo/plotEDFFile.py
@@ -1,12 +1,9 @@
 #!/usr/bin/env python
 
 import numpy as np
-
-import pyedflib
-
-
 from stacklineplot import stackplot
 
+import pyedflib
 
 if __name__ == '__main__':
     f = pyedflib.data.test_generator()
diff --git a/demo/readEDFFile.py b/demo/readEDFFile.py
index e770b8c..37415fe 100644
--- a/demo/readEDFFile.py
+++ b/demo/readEDFFile.py
@@ -1,11 +1,11 @@
 #!/usr/bin/env python
 
 import os
+
 import numpy as np
 
 import pyedflib
 
-
 if __name__ == '__main__':
     f = pyedflib.data.test_generator()
     print("\nlibrary version: %s" % pyedflib.version.version)
diff --git a/demo/stacklineplot.py b/demo/stacklineplot.py
index d6626f9..4df7706 100644
--- a/demo/stacklineplot.py
+++ b/demo/stacklineplot.py
@@ -2,8 +2,8 @@
 # uses line collections (might actually be from pbrain example)
 # clm
 
-import numpy as np
 import matplotlib.pyplot as plt
+import numpy as np
 from matplotlib.collections import LineCollection
 
 
diff --git a/demo/streamingEDFFile.py b/demo/streamingEDFFile.py
index d709161..e4845bc 100644
--- a/demo/streamingEDFFile.py
+++ b/demo/streamingEDFFile.py
@@ -1,12 +1,15 @@
 #!/usr/bin/env python
 
-import numpy as np
-import matplotlib.pyplot as plt
-import matplotlib.animation as animation
 import time
-import pyedflib
+
+import matplotlib.animation as animation
+import matplotlib.pyplot as plt
+import numpy as np
 from stacklineplot import stackplot_t
 
+import pyedflib
+
+
 def animate(frame):
     global offset
     for i in np.arange(n):
diff --git a/demo/writeEDFFile.py b/demo/writeEDFFile.py
index 2fbcd9f..1f21425 100644
--- a/demo/writeEDFFile.py
+++ b/demo/writeEDFFile.py
@@ -1,8 +1,10 @@
 # Copyright (c) 2016 Holger Nahrstaedt
 
 import os
+
 import numpy as np
 from scipy import signal
+
 import pyedflib
 
 # signal label/waveform  amplitude    f       sf
diff --git a/doc/source/conf.py b/doc/source/conf.py
index f09445e..b478635 100644
--- a/doc/source/conf.py
+++ b/doc/source/conf.py
@@ -9,10 +9,10 @@
 #
 # All configuration values have a default; values that are commented out
 # serve to show the default.
-import re
 import datetime
-import jinja2.filters
+import re
 
+import jinja2.filters
 import numpy as np
 
 # FIXME: doctests need the str/repr formatting used in Numpy < 1.14.
@@ -64,6 +64,7 @@
 #
 # The short X.Y version.
 import pyedflib
+
 version = re.sub(r'\.dev0+.*$', r'.dev', pyedflib.__version__)
 release = pyedflib.__version__
 
diff --git a/pyedflib/__init__.py b/pyedflib/__init__.py
index 60cb97b..bdadadb 100644
--- a/pyedflib/__init__.py
+++ b/pyedflib/__init__.py
@@ -6,12 +6,7 @@
 #                         <https://github.com/holgern/pyedflib>
 # See LICENSE for license details.
 
-from ._extensions._pyedflib import *
-from .edfwriter import *
-from .edfreader import *
-from . import highlevel
-
-from . import data
+from numpy.testing import Tester
 
 from pyedflib.version import version as __version__
 
diff --git a/pyedflib/_extensions/_pyedflib.pyx b/pyedflib/_extensions/_pyedflib.pyx
index 136daf5..fa99b74 100644
--- a/pyedflib/_extensions/_pyedflib.pyx
+++ b/pyedflib/_extensions/_pyedflib.pyx
@@ -21,12 +21,18 @@ __all__ = ['lib_version', 'CyEdfReader', 'set_patientcode', 'set_starttime_subse
 import locale
 import os
 import warnings
+
 cimport c_edf
 cimport cpython
+
 import numpy as np
+
 cimport numpy as np
-from datetime import datetime, date
+
+from datetime import date, datetime
+
 from cpython.version cimport PY_MAJOR_VERSION
+
 include "edf.pxi"
 
 open_errors = {
diff --git a/pyedflib/data/__init__.py b/pyedflib/data/__init__.py
index ee10415..f52b313 100644
--- a/pyedflib/data/__init__.py
+++ b/pyedflib/data/__init__.py
@@ -1 +1 @@
-from ._readers import test_generator, get_generator_filename
+from ._readers import get_generator_filename, test_generator
diff --git a/pyedflib/data/_readers.py b/pyedflib/data/_readers.py
index 7cb48a5..e38fcd1 100644
--- a/pyedflib/data/_readers.py
+++ b/pyedflib/data/_readers.py
@@ -1,6 +1,7 @@
 import os
 
 import numpy as np
+
 import pyedflib
 
 
diff --git a/pyedflib/edfreader.py b/pyedflib/edfreader.py
index 2730f62..193f108 100644
--- a/pyedflib/edfreader.py
+++ b/pyedflib/edfreader.py
@@ -6,6 +6,7 @@
 # See LICENSE for license details.
 
 from datetime import datetime
+
 import numpy as np
 
 from ._extensions._pyedflib import CyEdfReader
diff --git a/pyedflib/edfwriter.py b/pyedflib/edfwriter.py
index 6d99b83..3c971eb 100644
--- a/pyedflib/edfwriter.py
+++ b/pyedflib/edfwriter.py
@@ -5,18 +5,33 @@
 #                         <https://github.com/holgern/pyedflib>
 # See LICENSE for license details.
 
-import numpy as np
 import sys
 import warnings
-from datetime import datetime, date
-from ._extensions._pyedflib import FILETYPE_EDFPLUS, FILETYPE_BDFPLUS, FILETYPE_BDF, FILETYPE_EDF
-from ._extensions._pyedflib import open_file_writeonly, set_physical_maximum, set_patient_additional, set_digital_maximum
-from ._extensions._pyedflib import set_birthdate, set_digital_minimum, set_technician, set_recording_additional, set_patientname
-from ._extensions._pyedflib import set_patientcode, set_equipment, set_admincode, set_gender, set_datarecord_duration, set_number_of_annotation_signals
-from ._extensions._pyedflib import set_startdatetime, set_starttime_subsecond, set_samples_per_record, set_physical_minimum, set_label, set_physical_dimension
-from ._extensions._pyedflib import set_transducer, set_prefilter, write_physical_samples, close_file, write_annotation_latin1, write_annotation_utf8
-from ._extensions._pyedflib import blockwrite_physical_samples, write_errors, blockwrite_digital_samples, write_digital_short_samples, write_digital_samples, blockwrite_digital_short_samples
+from datetime import date, datetime
+
+import numpy as np
 
+from ._extensions._pyedflib import (FILETYPE_BDF, FILETYPE_BDFPLUS,
+                                    FILETYPE_EDF, FILETYPE_EDFPLUS,
+                                    blockwrite_digital_samples,
+                                    blockwrite_digital_short_samples,
+                                    blockwrite_physical_samples, close_file,
+                                    open_file_writeonly, set_admincode,
+                                    set_birthdate, set_datarecord_duration,
+                                    set_digital_maximum, set_digital_minimum,
+                                    set_equipment, set_gender, set_label,
+                                    set_number_of_annotation_signals,
+                                    set_patient_additional, set_patientcode,
+                                    set_patientname, set_physical_dimension,
+                                    set_physical_maximum, set_physical_minimum,
+                                    set_prefilter, set_recording_additional,
+                                    set_samples_per_record, set_startdatetime,
+                                    set_starttime_subsecond, set_technician,
+                                    set_transducer, write_annotation_latin1,
+                                    write_annotation_utf8,
+                                    write_digital_samples,
+                                    write_digital_short_samples, write_errors,
+                                    write_physical_samples)
 
 __all__ = ['EdfWriter']
 
diff --git a/pyedflib/highlevel.py b/pyedflib/highlevel.py
index e884814..d47e2c8 100644
--- a/pyedflib/highlevel.py
+++ b/pyedflib/highlevel.py
@@ -20,11 +20,14 @@
 """
 
 import os
-import numpy as np
 import warnings
-import pyedflib
 from copy import deepcopy
 from datetime import datetime
+
+import numpy as np
+
+import pyedflib
+
 # from . import EdfWriter
 # from . import EdfReader
 
diff --git a/pyedflib/tests/test_doc.py b/pyedflib/tests/test_doc.py
index 29b2e53..449104c 100644
--- a/pyedflib/tests/test_doc.py
+++ b/pyedflib/tests/test_doc.py
@@ -3,7 +3,6 @@
 import os
 import unittest
 
-
 pdir = os.path.pardir
 docs_base = os.path.abspath(os.path.join(os.path.dirname(__file__),
                                          pdir, pdir, "doc", "source"))
diff --git a/pyedflib/tests/test_edfreader.py b/pyedflib/tests/test_edfreader.py
index f1be587..d107e92 100644
--- a/pyedflib/tests/test_edfreader.py
+++ b/pyedflib/tests/test_edfreader.py
@@ -1,16 +1,18 @@
 # Copyright (c) 2019 - 2020 Simon Kern
 # Copyright (c) 2015 Holger Nahrstaedt
 
-import os
 import gc
-import numpy as np
-from datetime import datetime
+import os
 # from numpy.testing import (assert_raises, run_module_suite,
 #                            assert_equal, assert_allclose, assert_almost_equal)
 import unittest
+from datetime import datetime
+
+import numpy as np
+
 import pyedflib
-from pyedflib.edfwriter import EdfWriter
 from pyedflib.edfreader import EdfReader
+from pyedflib.edfwriter import EdfWriter
 
 
 class TestEdfReader(unittest.TestCase):
diff --git a/pyedflib/tests/test_edfwriter.py b/pyedflib/tests/test_edfwriter.py
index ad8456a..0f56558 100644
--- a/pyedflib/tests/test_edfwriter.py
+++ b/pyedflib/tests/test_edfwriter.py
@@ -1,16 +1,18 @@
 # Copyright (c) 2019 - 2023 Simon Kern
 # Copyright (c) 2015 Holger Nahrstaedt
 
-import os
 import gc
-import numpy as np
+import os
 # from numpy.testing import (assert_raises, run_module_suite,
 #                            assert_equal, assert_allclose, assert_almost_equal)
 import unittest
+from datetime import date, datetime
+
+import numpy as np
+
 import pyedflib
-from pyedflib.edfwriter import EdfWriter, ChannelDoesNotExist, WrongInputSize
 from pyedflib.edfreader import EdfReader
-from datetime import datetime, date
+from pyedflib.edfwriter import ChannelDoesNotExist, EdfWriter, WrongInputSize
 
 
 class TestEdfWriter(unittest.TestCase):
diff --git a/pyedflib/tests/test_highlevel.py b/pyedflib/tests/test_highlevel.py
index aaf527a..be4435c 100644
--- a/pyedflib/tests/test_highlevel.py
+++ b/pyedflib/tests/test_highlevel.py
@@ -1,17 +1,21 @@
 # Copyright (c) 2019 - 2020 Simon Kern
 # Copyright (c) 2015 Holger Nahrstaedt
 
-import os, sys
-import shutil
 import gc
-import numpy as np
+import os
+import shutil
+import sys
 # from numpy.testing import (assert_raises, run_module_suite,
 #                            assert_equal, assert_allclose, assert_almost_equal)
 import unittest
+from datetime import date, datetime
+
+import numpy as np
+
 from pyedflib import highlevel
-from pyedflib.edfwriter import EdfWriter
 from pyedflib.edfreader import EdfReader
-from datetime import datetime, date
+from pyedflib.edfwriter import EdfWriter
+
 
 class TestHighLevel(unittest.TestCase):
 
diff --git a/setup.py b/setup.py
index ea2d495..2c9cbd2 100644
--- a/setup.py
+++ b/setup.py
@@ -1,13 +1,13 @@
 #!/usr/bin/env python
 
 import os
-import sys
 import subprocess
-import setuptools
+import sys
+from distutils.sysconfig import get_python_inc
 from functools import partial
 
-from setuptools import setup, Extension
-from distutils.sysconfig import get_python_inc
+import setuptools
+from setuptools import Extension, setup
 
 try:
     from Cython.Build import cythonize
@@ -213,6 +213,8 @@ def write_version_py(filename='pyedflib/version.py'):
 ]
 
 from setuptools.command.develop import develop
+
+
 class develop_build_clib(develop):
     """Ugly monkeypatching to get clib to build for development installs
     See coverage comment above for why we don't just let libraries be built
diff --git a/util/authors.py b/util/authors.py
index 90451ae..7e31c02 100644
--- a/util/authors.py
+++ b/util/authors.py
@@ -13,13 +13,11 @@
 """
 # Author: Pauli Virtanen <pav@iki.fi>. This script is in the public domain.
 
+import collections
+import io
 import optparse
-import re
-import sys
 import os
-import io
 import subprocess
-import collections
 
 stdout_b = sys.stdout.buffer
 MAILMAP_FILE = os.path.join(os.path.dirname(__file__), "..", ".mailmap")
diff --git a/util/gh_lists.py b/util/gh_lists.py
index 786ef8f..e483ea5 100644
--- a/util/gh_lists.py
+++ b/util/gh_lists.py
@@ -4,16 +4,15 @@
 
 Functions for Github API requests.
 """
+import argparse
+import collections
+import json
 import os
 import re
 import sys
-import json
-import collections
-import argparse
 
 from urllib2 import urlopen
 
-
 Issue = collections.namedtuple('Issue', ('id', 'title', 'url'))
 
 
diff --git a/util/refguide_check.py b/util/refguide_check.py
index fc932cc..0652be4 100644
--- a/util/refguide_check.py
+++ b/util/refguide_check.py
@@ -22,26 +22,27 @@
     $ python refguide_check.py --check_docs optimize
 
 """
-import sys
-import os
-import re
 import copy
-import inspect
-import warnings
 import doctest
-import tempfile
+import glob
+import inspect
 import io
-import docutils.core
-from docutils.parsers.rst import directives
+import os
+import re
 import shutil
-import glob
-from doctest import NORMALIZE_WHITESPACE, ELLIPSIS, IGNORE_EXCEPTION_DETAIL
+import sys
+import tempfile
+import warnings
 from argparse import ArgumentParser
-import numpy as np
+from doctest import ELLIPSIS, IGNORE_EXCEPTION_DETAIL, NORMALIZE_WHITESPACE
 
+import docutils.core
+import numpy as np
+from docutils.parsers.rst import directives
 # sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..', 'doc',
 #                 'sphinxext'))
 from numpydoc.docscrape_sphinx import get_doc_object
+
 # Remove sphinx directives that don't run without Sphinx environment
 directives._directives.pop('versionadded', None)
 directives._directives.pop('versionchanged', None)