diff --git a/qurator/dinglehopper/__init__.py b/qurator/dinglehopper/__init__.py
index f883dfc..e69de29 100644
--- a/qurator/dinglehopper/__init__.py
+++ b/qurator/dinglehopper/__init__.py
@@ -1,3 +0,0 @@
-from .ocr_files import *
-from .extracted_text import *
-from .align import *
diff --git a/qurator/dinglehopper/align.py b/qurator/dinglehopper/align.py
index cc7230b..cc35c63 100644
--- a/qurator/dinglehopper/align.py
+++ b/qurator/dinglehopper/align.py
@@ -1,4 +1,4 @@
-from .edit_distance import *
+from .edit_distance import seq_editops
 from .normalize import chars_normalized
 
 
diff --git a/qurator/dinglehopper/cli.py b/qurator/dinglehopper/cli.py
index 8452fa8..dbf9b28 100644
--- a/qurator/dinglehopper/cli.py
+++ b/qurator/dinglehopper/cli.py
@@ -36,13 +36,9 @@ def gen_diff_report(gt_in, ocr_in, css_prefix, joiner, none):
             html_custom_attrs += 'data-toggle="tooltip" title="{}"'.format(id_)
 
         if css_classes:
-            return '<span class="{css_classes}" {html_custom_attrs}>{html_t}</span>'.format(
-                css_classes=css_classes,
-                html_t=html_t,
-                html_custom_attrs=html_custom_attrs,
-            )
+            return f"<span class=\"{css_classes}\" {html_custom_attrs}>{html_t}</span>"
         else:
-            return "{html_t}".format(html_t=html_t)
+            return f"{html_t}"
 
     if isinstance(gt_in, ExtractedText):
         if not isinstance(ocr_in, ExtractedText):
diff --git a/qurator/dinglehopper/cli_extract.py b/qurator/dinglehopper/cli_extract.py
index 0d4f713..9c51d34 100644
--- a/qurator/dinglehopper/cli_extract.py
+++ b/qurator/dinglehopper/cli_extract.py
@@ -1,9 +1,6 @@
-import os
-
 import click
 from ocrd_utils import initLogging
 
-from .extracted_text import ExtractedText
 from .ocr_files import extract
 
 
diff --git a/qurator/dinglehopper/edit_distance.py b/qurator/dinglehopper/edit_distance.py
index 798419c..91966a3 100644
--- a/qurator/dinglehopper/edit_distance.py
+++ b/qurator/dinglehopper/edit_distance.py
@@ -12,15 +12,16 @@ from .normalize import chars_normalized
 
 def levenshtein_matrix(seq1: Sequence, seq2: Sequence):
     """Compute the matrix commonly computed to produce the Levenshtein distance.
-    This is also known as the Wagner-Fischer algorithm. The matrix element at the bottom right contains the desired
-    edit distance.
+    This is also known as the Wagner-Fischer algorithm. The matrix element at the bottom
+    right contains the desired edit distance.
 
-    This algorithm is implemented here because we need an implementation that can work with sequences other than
-    strings, e.g. lists of grapheme clusters or lists of word strings.
+    This algorithm is implemented here because we need an implementation that can work
+    with sequences other than strings, e.g. lists of grapheme clusters or lists of word
+    strings.
     """
 
-    # Internally, we use a cached version. As the cache only works on hashable parameters, we convert the input
-    # sequences to tuples to make them hashable.
+    # Internally, we use a cached version. As the cache only works on hashable
+    # parameters, we convert the input sequences to tuples to make them hashable.
     return _levenshtein_matrix(tuple(seq1), tuple(seq2))
 
 
@@ -28,7 +29,8 @@ def levenshtein_matrix(seq1: Sequence, seq2: Sequence):
 def _levenshtein_matrix(seq1: Tuple, seq2: Tuple):
     """Compute the matrix commonly computed to produce the Levenshtein distance.
 
-    This is a LRU cached function not meant to be used directly. Use levenshtein_matrix() instead.
+    This is a LRU cached function not meant to be used directly.
+    Use levenshtein_matrix() instead.
     """
     m = len(seq1)
     n = len(seq2)
@@ -36,7 +38,7 @@ def _levenshtein_matrix(seq1: Tuple, seq2: Tuple):
     def from_to(start, stop):
         return range(start, stop + 1, 1)
 
-    D = np.zeros((m + 1, n + 1), np.int)
+    D = np.zeros((m + 1, n + 1), int)
     D[0, 0] = 0
     for i in from_to(1, m):
         D[i, 0] = i
@@ -75,8 +77,9 @@ def levenshtein_matrix_cache_clear():
 def distance(s1: str, s2: str):
     """Compute the Levenshtein edit distance between two Unicode strings
 
-    Note that this is different from levenshtein() as this function knows about Unicode normalization and grapheme
-    clusters. This should be the correct way to compare two Unicode strings.
+    Note that this is different from levenshtein() as this function knows about Unicode
+    normalization and grapheme clusters. This should be the correct way to compare two
+    Unicode strings.
     """
     seq1 = chars_normalized(s1)
     seq2 = chars_normalized(s2)
@@ -87,8 +90,8 @@ def seq_editops(seq1, seq2):
     """
     Return sequence of edit operations transforming one sequence to another.
 
-    This aims to return the same/similar results as python-Levenshtein's editops(), just generalized to arbitrary
-    sequences.
+    This aims to return the same/similar results as python-Levenshtein's editops(),
+    just generalized to arbitrary sequences.
     """
     seq1 = list(seq1)
     seq2 = list(seq2)
diff --git a/qurator/dinglehopper/metrics/__init__.py b/qurator/dinglehopper/metrics/__init__.py
index 07bb077..347d042 100644
--- a/qurator/dinglehopper/metrics/__init__.py
+++ b/qurator/dinglehopper/metrics/__init__.py
@@ -1,5 +1,14 @@
-from .bag_of_chars_accuracy import *
-from .bag_of_words_accuracy import *
-from .character_accuracy import *
+from .bag_of_chars_accuracy import bag_of_chars_accuracy
+from .bag_of_words_accuracy import bag_of_words_accuracy
+from .character_accuracy import character_accuracy
 from .utils import MetricResult, Weights
-from .word_accuracy import *
+from .word_accuracy import word_accuracy
+
+__all__ = [
+    "bag_of_chars_accuracy",
+    "bag_of_words_accuracy",
+    "character_accuracy",
+    "word_accuracy",
+    "MetricResult",
+    "Weights",
+]
diff --git a/qurator/dinglehopper/metrics/bag_of_chars_accuracy.py b/qurator/dinglehopper/metrics/bag_of_chars_accuracy.py
index 79ed34e..a6c8813 100644
--- a/qurator/dinglehopper/metrics/bag_of_chars_accuracy.py
+++ b/qurator/dinglehopper/metrics/bag_of_chars_accuracy.py
@@ -9,9 +9,8 @@ from .utils import bag_accuracy, MetricResult, Weights
 def bag_of_chars_accuracy(
     reference: str, compared: str, weights: Weights = Weights(1, 0, 1)
 ) -> MetricResult:
-    reference_chars = Counter(grapheme_clusters(normalize("NFC", reference)))
-    compared_chars = Counter(grapheme_clusters(normalize("NFC", compared)))
-    result = bag_accuracy(reference_chars, compared_chars, weights)
-    return MetricResult(
-        **{**result._asdict(), "metric": bag_of_chars_accuracy.__name__}
+    reference_chars: Counter = Counter(grapheme_clusters(normalize("NFC", reference)))
+    compared_chars: Counter = Counter(grapheme_clusters(normalize("NFC", compared)))
+    return bag_accuracy(
+        reference_chars, compared_chars, weights, bag_of_chars_accuracy.__name__
     )
diff --git a/qurator/dinglehopper/metrics/bag_of_words_accuracy.py b/qurator/dinglehopper/metrics/bag_of_words_accuracy.py
index f2e0a88..2426496 100644
--- a/qurator/dinglehopper/metrics/bag_of_words_accuracy.py
+++ b/qurator/dinglehopper/metrics/bag_of_words_accuracy.py
@@ -7,9 +7,8 @@ from ..normalize import words_normalized
 def bag_of_words_accuracy(
     reference: str, compared: str, weights: Weights = Weights(1, 0, 1)
 ) -> MetricResult:
-    reference_words = Counter(words_normalized(reference))
-    compared_words = Counter(words_normalized(compared))
-    result = bag_accuracy(reference_words, compared_words, weights)
-    return MetricResult(
-        **{**result._asdict(), "metric": bag_of_words_accuracy.__name__}
+    reference_words: Counter = Counter(words_normalized(reference))
+    compared_words: Counter = Counter(words_normalized(compared))
+    return bag_accuracy(
+        reference_words, compared_words, weights, bag_of_words_accuracy.__name__
     )
diff --git a/qurator/dinglehopper/metrics/character_accuracy.py b/qurator/dinglehopper/metrics/character_accuracy.py
index 1e89a76..abe4e4f 100644
--- a/qurator/dinglehopper/metrics/character_accuracy.py
+++ b/qurator/dinglehopper/metrics/character_accuracy.py
@@ -1,7 +1,5 @@
-from __future__ import division
-
 from .utils import MetricResult, Weights
-from .. import distance
+from ..edit_distance import distance
 from ..normalize import chars_normalized
 
 
diff --git a/qurator/dinglehopper/metrics/utils.py b/qurator/dinglehopper/metrics/utils.py
index 179f462..33469be 100644
--- a/qurator/dinglehopper/metrics/utils.py
+++ b/qurator/dinglehopper/metrics/utils.py
@@ -37,10 +37,7 @@ class MetricResult(NamedTuple):
         We deviate from the builtin _asdict() function by including our properties.
         """
         return {
-            **{
-                key: value
-                for key, value in self._asdict().items()
-            },
+            **{key: value for key, value in self._asdict().items()},
             "accuracy": self.accuracy,
             "error_rate": self.error_rate,
             "weights": self.weights._asdict(),
@@ -48,7 +45,10 @@ class MetricResult(NamedTuple):
 
 
 def bag_accuracy(
-    reference: Counter, compared: Counter, weights: Weights
+    reference: Counter,
+    compared: Counter,
+    weights: Weights,
+    metric: str = "bag_accuracy",
 ) -> MetricResult:
     """Calculates the the weighted errors for two bags (Counter).
 
@@ -61,6 +61,7 @@ def bag_accuracy(
     :param reference: Bag used as reference (ground truth).
     :param compared: Bag used to compare (ocr).
     :param weights: Weights/costs for editing operations.
+    :param metric: Name of the (original) metric.
     :return: NamedTuple representing the results of this metric.
     """
     n_ref = sum(reference.values())
@@ -77,7 +78,7 @@ def bag_accuracy(
         + weights.replacements * replacements
     )
     return MetricResult(
-        metric=bag_accuracy.__name__,
+        metric=metric,
         weights=weights,
         weighted_errors=weighted_errors,
         reference_elements=n_ref,
diff --git a/qurator/dinglehopper/normalize.py b/qurator/dinglehopper/normalize.py
index 4ae6617..14eefbc 100644
--- a/qurator/dinglehopper/normalize.py
+++ b/qurator/dinglehopper/normalize.py
@@ -1,26 +1,19 @@
 import unicodedata
-from typing import Union
 
 import uniseg.wordbreak
 from uniseg.graphemecluster import grapheme_clusters
 
-from .extracted_text import ExtractedText
 
-
-def chars_normalized(s: Union[str, ExtractedText]):
+def chars_normalized(s: str):
     """Normalize characters in string."""
-    if isinstance(s, ExtractedText):
-        s = s.text
     return list(grapheme_clusters(unicodedata.normalize("NFC", s)))
 
 
-def words(s: Union[str, ExtractedText]):
+def words(s: str):
     """Extract words from a string"""
 
-    if isinstance(s, ExtractedText):
-        s = s.text
-
-    # Patch uniseg.wordbreak.word_break to deal with our private use characters. See also
+    # Patch uniseg.wordbreak.word_break to deal with our private use characters.
+    # See also
     # https://www.unicode.org/Public/UCD/latest/ucd/auxiliary/WordBreakProperty.txt
     old_word_break = uniseg.wordbreak.word_break
 
@@ -54,8 +47,6 @@ def words(s: Union[str, ExtractedText]):
             yield word
 
 
-def words_normalized(s: Union[str, ExtractedText]):
+def words_normalized(s: str):
     """Extract words from string and normalize them."""
-    if isinstance(s, ExtractedText):
-        s = s.text
     return words(unicodedata.normalize("NFC", s))
diff --git a/qurator/dinglehopper/ocr_files.py b/qurator/dinglehopper/ocr_files.py
index 1f319f5..0eab0c5 100644
--- a/qurator/dinglehopper/ocr_files.py
+++ b/qurator/dinglehopper/ocr_files.py
@@ -1,7 +1,4 @@
-from __future__ import division, print_function
-
 from typing import Iterator
-from warnings import warn
 import sys
 
 from lxml import etree as ET
@@ -13,7 +10,8 @@ from .extracted_text import ExtractedText, normalize_sbb
 def alto_namespace(tree: ET.ElementTree) -> str:
     """Return the ALTO namespace used in the given ElementTree.
 
-    This relies on the assumption that, in any given ALTO file, the root element has the local name "alto". We do not
+    This relies on the assumption that, in any given ALTO file,
+    the root element has the local name "alto". We do not
     check if the files uses any valid ALTO namespace.
     """
     root_name = ET.QName(tree.getroot().tag)
@@ -47,8 +45,9 @@ def alto_text(tree):
 def page_namespace(tree):
     """Return the PAGE content namespace used in the given ElementTree.
 
-    This relies on the assumption that, in any given PAGE content file, the root element has the local name "PcGts". We
-    do not check if the files uses any valid PAGE namespace.
+    This relies on the assumption that, in any given PAGE content file,
+    the root element has the local name "PcGts".
+    We do not check if the files uses any valid PAGE namespace.
     """
     root_name = ET.QName(tree.getroot().tag)
     if root_name.localname == "PcGts":
@@ -97,14 +96,18 @@ def extract_texts_from_reading_order_group(group, tree, nsmap, textequiv_level):
 
         ro_children = filter(lambda child: "index" in child.attrib.keys(), ro_children)
         ro_children = sorted(ro_children, key=lambda child: int(child.attrib["index"]))
-    elif ET.QName(group.tag).localname in ["UnorderedGroup","UnorderedGroupIndexed"]:
+    elif ET.QName(group.tag).localname in ["UnorderedGroup", "UnorderedGroupIndexed"]:
         ro_children = list(group)
     else:
         raise NotImplementedError
 
-
     for ro_child in ro_children:
-        if ET.QName(ro_child.tag).localname in ["OrderedGroup", "OrderedGroupIndexed", "UnorderedGroup", "UnorderedGroupIndexed"]:
+        if ET.QName(ro_child.tag).localname in [
+            "OrderedGroup",
+            "OrderedGroupIndexed",
+            "UnorderedGroup",
+            "UnorderedGroupIndexed",
+        ]:
             regions.extend(
                 extract_texts_from_reading_order_group(
                     ro_child, tree, nsmap, textequiv_level
diff --git a/qurator/dinglehopper/ocrd_cli.py b/qurator/dinglehopper/ocrd_cli.py
index adfbbab..c7aea19 100644
--- a/qurator/dinglehopper/ocrd_cli.py
+++ b/qurator/dinglehopper/ocrd_cli.py
@@ -77,5 +77,6 @@ class OcrdDinglehopperEvaluate(Processor):
             # Clear cache between files
             levenshtein_matrix_cache_clear()
 
+
 if __name__ == "__main__":
     ocrd_dinglehopper()
diff --git a/qurator/dinglehopper/tests/extracted_text_test.py b/qurator/dinglehopper/tests/extracted_text_test.py
index 8a81587..c5301ec 100644
--- a/qurator/dinglehopper/tests/extracted_text_test.py
+++ b/qurator/dinglehopper/tests/extracted_text_test.py
@@ -6,7 +6,8 @@ import pytest
 from lxml import etree as ET
 from uniseg.graphemecluster import grapheme_clusters
 
-from .. import seq_align, ExtractedText
+from ..align import seq_align
+from ..extracted_text import ExtractedText
 
 
 def test_text():
diff --git a/qurator/dinglehopper/tests/metrics/test_integ_character_accuracy_ocr.py b/qurator/dinglehopper/tests/metrics/test_integ_character_accuracy_ocr.py
index b12c08c..9dcd0db 100644
--- a/qurator/dinglehopper/tests/metrics/test_integ_character_accuracy_ocr.py
+++ b/qurator/dinglehopper/tests/metrics/test_integ_character_accuracy_ocr.py
@@ -6,8 +6,8 @@ import pytest
 from lxml import etree as ET
 from uniseg.graphemecluster import grapheme_clusters
 
-from ... import page_text, alto_text
 from ...metrics import character_accuracy
+from ...ocr_files import alto_text, page_text
 
 data_dir = os.path.join(os.path.dirname(os.path.abspath(__file__)), "../", "data")
 
diff --git a/qurator/dinglehopper/tests/metrics/test_integ_word_accuracy.py b/qurator/dinglehopper/tests/metrics/test_integ_word_accuracy.py
index 849dc99..99169de 100644
--- a/qurator/dinglehopper/tests/metrics/test_integ_word_accuracy.py
+++ b/qurator/dinglehopper/tests/metrics/test_integ_word_accuracy.py
@@ -5,9 +5,9 @@ import os
 import pytest
 from lxml import etree as ET
 
-from ... import alto_text, page_text
 from ...metrics import word_accuracy
 from ...normalize import words
+from ...ocr_files import alto_text, page_text
 
 data_dir = os.path.join(os.path.dirname(os.path.abspath(__file__)), "../", "data")
 
diff --git a/qurator/dinglehopper/tests/test_align.py b/qurator/dinglehopper/tests/test_align.py
index 9f9d926..4ecbda2 100644
--- a/qurator/dinglehopper/tests/test_align.py
+++ b/qurator/dinglehopper/tests/test_align.py
@@ -1,5 +1,6 @@
 from .util import unzip
-from .. import align, seq_align, distance
+from ..align import align, seq_align
+from ..edit_distance import distance
 
 
 def test_left_empty():
diff --git a/qurator/dinglehopper/tests/test_edit_distance.py b/qurator/dinglehopper/tests/test_edit_distance.py
index dc1f202..b1ad47f 100644
--- a/qurator/dinglehopper/tests/test_edit_distance.py
+++ b/qurator/dinglehopper/tests/test_edit_distance.py
@@ -1,8 +1,6 @@
-from __future__ import division, print_function
-
 import unicodedata
 
-from .. import levenshtein, distance
+from ..edit_distance import levenshtein, distance
 
 
 def test_levenshtein():
diff --git a/qurator/dinglehopper/tests/test_editops.py b/qurator/dinglehopper/tests/test_editops.py
index 06afbfc..b27fcd8 100644
--- a/qurator/dinglehopper/tests/test_editops.py
+++ b/qurator/dinglehopper/tests/test_editops.py
@@ -1,6 +1,6 @@
 import unicodedata
 
-from .. import seq_editops, editops
+from ..edit_distance import seq_editops, editops
 
 
 def test_trivial():
diff --git a/qurator/dinglehopper/tests/test_integ_align.py b/qurator/dinglehopper/tests/test_integ_align.py
index 74b8c7e..4ab2eac 100644
--- a/qurator/dinglehopper/tests/test_integ_align.py
+++ b/qurator/dinglehopper/tests/test_integ_align.py
@@ -1,11 +1,10 @@
-from __future__ import division, print_function
-
 import os
 
 import pytest
 from lxml import etree as ET
 
-from .. import align, page_text
+from ..align import align
+from ..ocr_files import page_text
 
 data_dir = os.path.join(os.path.dirname(os.path.abspath(__file__)), "data")
 
diff --git a/qurator/dinglehopper/tests/test_integ_edit_distance_ocr.py b/qurator/dinglehopper/tests/test_integ_edit_distance_ocr.py
index 0e1e7da..8bfbad8 100644
--- a/qurator/dinglehopper/tests/test_integ_edit_distance_ocr.py
+++ b/qurator/dinglehopper/tests/test_integ_edit_distance_ocr.py
@@ -5,7 +5,8 @@ import os
 import pytest
 from lxml import etree as ET
 
-from .. import distance, page_text, alto_text
+from ..edit_distance import distance
+from ..ocr_files import alto_text, page_text
 
 data_dir = os.path.join(os.path.dirname(os.path.abspath(__file__)), "data")
 
diff --git a/qurator/dinglehopper/tests/test_integ_table_extraction.py b/qurator/dinglehopper/tests/test_integ_table_extraction.py
index 868308c..b7703bb 100644
--- a/qurator/dinglehopper/tests/test_integ_table_extraction.py
+++ b/qurator/dinglehopper/tests/test_integ_table_extraction.py
@@ -3,7 +3,7 @@ import os
 import pytest
 from lxml import etree as ET
 
-from .. import page_text
+from ..ocr_files import page_text
 
 
 @pytest.mark.parametrize(
diff --git a/qurator/dinglehopper/tests/test_ocr_files.py b/qurator/dinglehopper/tests/test_ocr_files.py
index fb38c4a..f48c59c 100644
--- a/qurator/dinglehopper/tests/test_ocr_files.py
+++ b/qurator/dinglehopper/tests/test_ocr_files.py
@@ -1,13 +1,12 @@
 import os
 import re
-
-import lxml.etree as ET
 import textwrap
 
-import pytest
+import lxml.etree as ET
 
 from .util import working_directory
-from .. import alto_namespace, alto_text, page_namespace, page_text, plain_text, text
+from ..ocr_files import alto_namespace, alto_text, page_namespace, page_text, \
+    plain_text, text
 
 data_dir = os.path.join(os.path.dirname(os.path.abspath(__file__)), "data")