diff --git a/cssutils/_fetch.py b/cssutils/_fetch.py
index 9c6f5668..e3c6be9b 100644
--- a/cssutils/_fetch.py
+++ b/cssutils/_fetch.py
@@ -17,7 +17,7 @@
 log = errorhandler.ErrorHandler()
 
 
-@functools.lru_cache()
+@functools.lru_cache
 def _get_version():
     try:
         return metadata.version('cssutils')
diff --git a/cssutils/css/csscharsetrule.py b/cssutils/css/csscharsetrule.py
index a0e537f1..6fd7e558 100644
--- a/cssutils/css/csscharsetrule.py
+++ b/cssutils/css/csscharsetrule.py
@@ -58,16 +58,10 @@ def __init__(
         self._readonly = readonly
 
     def __repr__(self):
-        return "cssutils.css.{}(encoding={!r})".format(
-            self.__class__.__name__, self.encoding
-        )
+        return f"cssutils.css.{self.__class__.__name__}(encoding={self.encoding!r})"
 
     def __str__(self):
-        return "<cssutils.css.{} object encoding={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.encoding,
-            id(self),
-        )
+        return f"<cssutils.css.{self.__class__.__name__} object encoding={self.encoding!r} at 0x{id(self):x}>"
 
     def _getCssText(self):
         """The parsable textual representation."""
diff --git a/cssutils/css/csscomment.py b/cssutils/css/csscomment.py
index 9a8f4dd3..de12fd46 100644
--- a/cssutils/css/csscomment.py
+++ b/cssutils/css/csscomment.py
@@ -32,16 +32,10 @@ def __init__(
         self._readonly = readonly
 
     def __repr__(self):
-        return "cssutils.css.{}(cssText={!r})".format(
-            self.__class__.__name__, self.cssText
-        )
+        return f"cssutils.css.{self.__class__.__name__}(cssText={self.cssText!r})"
 
     def __str__(self):
-        return "<cssutils.css.{} object cssText={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.cssText,
-            id(self),
-        )
+        return f"<cssutils.css.{self.__class__.__name__} object cssText={self.cssText!r} at 0x{id(self):x}>"
 
     def _getCssText(self):
         """Return serialized property cssText."""
diff --git a/cssutils/css/cssfontfacerule.py b/cssutils/css/cssfontfacerule.py
index c7420444..e25c440f 100644
--- a/cssutils/css/cssfontfacerule.py
+++ b/cssutils/css/cssfontfacerule.py
@@ -52,18 +52,10 @@ def __init__(
         self._readonly = readonly
 
     def __repr__(self):
-        return "cssutils.css.{}(style={!r})".format(
-            self.__class__.__name__,
-            self.style.cssText,
-        )
+        return f"cssutils.css.{self.__class__.__name__}(style={self.style.cssText!r})"
 
     def __str__(self):
-        return "<cssutils.css.{} object style={!r} valid={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.style.cssText,
-            self.valid,
-            id(self),
-        )
+        return f"<cssutils.css.{self.__class__.__name__} object style={self.style.cssText!r} valid={self.valid!r} at 0x{id(self):x}>"
 
     def _getCssText(self):
         """Return serialized property cssText."""
diff --git a/cssutils/css/cssimportrule.py b/cssutils/css/cssimportrule.py
index d9915a3b..f4bbc780 100644
--- a/cssutils/css/cssimportrule.py
+++ b/cssutils/css/cssimportrule.py
@@ -75,25 +75,14 @@ def __repr__(self):
             mediaText = self.media.mediaText
         else:
             mediaText = None
-        return "cssutils.css.{}(href={!r}, mediaText={!r}, name={!r})".format(
-            self.__class__.__name__,
-            self.href,
-            mediaText,
-            self.name,
-        )
+        return f"cssutils.css.{self.__class__.__name__}(href={self.href!r}, mediaText={mediaText!r}, name={self.name!r})"
 
     def __str__(self):
         if self._usemedia:
             mediaText = self.media.mediaText
         else:
             mediaText = None
-        return "<cssutils.css.{} object href={!r} mediaText={!r} name={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.href,
-            mediaText,
-            self.name,
-            id(self),
-        )
+        return f"<cssutils.css.{self.__class__.__name__} object href={self.href!r} mediaText={mediaText!r} name={self.name!r} at 0x{id(self):x}>"
 
     _usemedia = property(
         lambda self: self.media.mediaText not in ('', 'all'),
diff --git a/cssutils/css/cssmediarule.py b/cssutils/css/cssmediarule.py
index 19d7684d..979b9bfa 100644
--- a/cssutils/css/cssmediarule.py
+++ b/cssutils/css/cssmediarule.py
@@ -47,17 +47,10 @@ def __init__(
         self._readonly = readonly
 
     def __repr__(self):
-        return "cssutils.css.{}(mediaText={!r})".format(
-            self.__class__.__name__,
-            self.media.mediaText,
-        )
+        return f"cssutils.css.{self.__class__.__name__}(mediaText={self.media.mediaText!r})"
 
     def __str__(self):
-        return "<cssutils.css.{} object mediaText={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.media.mediaText,
-            id(self),
-        )
+        return f"<cssutils.css.{self.__class__.__name__} object mediaText={self.media.mediaText!r} at 0x{id(self):x}>"
 
     def _getCssText(self):
         """Return serialized property cssText."""
diff --git a/cssutils/css/cssnamespacerule.py b/cssutils/css/cssnamespacerule.py
index 4af372a9..b687b458 100644
--- a/cssutils/css/cssnamespacerule.py
+++ b/cssutils/css/cssnamespacerule.py
@@ -89,20 +89,11 @@ def __init__(
         self._readonly = readonly
 
     def __repr__(self):
-        return "cssutils.css.{}(namespaceURI={!r}, prefix={!r})".format(
-            self.__class__.__name__,
-            self.namespaceURI,
-            self.prefix,
-        )
+        return f"cssutils.css.{self.__class__.__name__}(namespaceURI={self.namespaceURI!r}, prefix={self.prefix!r})"
 
     def __str__(self):
         return (
-            "<cssutils.css.{} object namespaceURI={!r} prefix={!r} at 0x{:x}>".format(
-                self.__class__.__name__,
-                self.namespaceURI,
-                self.prefix,
-                id(self),
-            )
+            f"<cssutils.css.{self.__class__.__name__} object namespaceURI={self.namespaceURI!r} prefix={self.prefix!r} at 0x{id(self):x}>"
         )
 
     def _getCssText(self):
diff --git a/cssutils/css/csspagerule.py b/cssutils/css/csspagerule.py
index fa83c7cb..f236f06d 100644
--- a/cssutils/css/csspagerule.py
+++ b/cssutils/css/csspagerule.py
@@ -93,11 +93,7 @@ def __init__(
         self._readonly = readonly
 
     def __repr__(self):
-        return "cssutils.css.{}(selectorText={!r}, style={!r})".format(
-            self.__class__.__name__,
-            self.selectorText,
-            self.style.cssText,
-        )
+        return f"cssutils.css.{self.__class__.__name__}(selectorText={self.selectorText!r}, style={self.style.cssText!r})"
 
     def __str__(self):
         return (
diff --git a/cssutils/css/cssrule.py b/cssutils/css/cssrule.py
index 3b701733..d74f9b42 100644
--- a/cssutils/css/cssrule.py
+++ b/cssutils/css/cssrule.py
@@ -79,9 +79,7 @@ def _setAtkeyword(self, keyword):
             self._keyword = keyword
         else:
             self._log.error(
-                '{}: Invalid atkeyword for this rule: {!r}'.format(
-                    self.atkeyword, keyword
-                ),
+                f'{self.atkeyword}: Invalid atkeyword for this rule: {keyword!r}',
                 error=xml.dom.InvalidModificationErr,
             )
 
diff --git a/cssutils/css/cssstyledeclaration.py b/cssutils/css/cssstyledeclaration.py
index 558c4956..ce1811b9 100644
--- a/cssutils/css/cssstyledeclaration.py
+++ b/cssutils/css/cssstyledeclaration.py
@@ -208,12 +208,7 @@ def __repr__(self):
         )
 
     def __str__(self):
-        return "<cssutils.css.{} object length={!r} (all: {!r}) at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.length,
-            len(self.getProperties(all=True)),
-            id(self),
-        )
+        return f"<cssutils.css.{self.__class__.__name__} object length={self.length!r} (all: {len(self.getProperties(all=True))!r}) at 0x{id(self):x}>"
 
     def __nnames(self):
         """Return iterator for all different names in order as set
diff --git a/cssutils/css/cssstylerule.py b/cssutils/css/cssstylerule.py
index 79193ae5..092ff96c 100644
--- a/cssutils/css/cssstylerule.py
+++ b/cssutils/css/cssstylerule.py
@@ -56,11 +56,7 @@ def __repr__(self):
             st = (self.selectorText, self._namespaces)
         else:
             st = self.selectorText
-        return "cssutils.css.{}(selectorText={!r}, style={!r})".format(
-            self.__class__.__name__,
-            st,
-            self.style.cssText,
-        )
+        return f"cssutils.css.{self.__class__.__name__}(selectorText={st!r}, style={self.style.cssText!r})"
 
     def __str__(self):
         return (
diff --git a/cssutils/css/cssstylesheet.py b/cssutils/css/cssstylesheet.py
index c8aa3735..f17e4800 100644
--- a/cssutils/css/cssstylesheet.py
+++ b/cssutils/css/cssstylesheet.py
@@ -78,12 +78,7 @@ def __repr__(self):
             mediaText = self.media.mediaText
         else:
             mediaText = None
-        return "cssutils.css.{}(href={!r}, media={!r}, title={!r})".format(
-            self.__class__.__name__,
-            self.href,
-            mediaText,
-            self.title,
-        )
+        return f"cssutils.css.{self.__class__.__name__}(href={self.href!r}, media={mediaText!r}, title={self.title!r})"
 
     def __str__(self):
         if self.media:
diff --git a/cssutils/css/cssunknownrule.py b/cssutils/css/cssunknownrule.py
index 8ad2c7ad..3f8650c0 100644
--- a/cssutils/css/cssunknownrule.py
+++ b/cssutils/css/cssunknownrule.py
@@ -32,16 +32,10 @@ def __init__(
         self._readonly = readonly
 
     def __repr__(self):
-        return "cssutils.css.{}(cssText={!r})".format(
-            self.__class__.__name__, self.cssText
-        )
+        return f"cssutils.css.{self.__class__.__name__}(cssText={self.cssText!r})"
 
     def __str__(self):
-        return "<cssutils.css.{} object cssText={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.cssText,
-            id(self),
-        )
+        return f"<cssutils.css.{self.__class__.__name__} object cssText={self.cssText!r} at 0x{id(self):x}>"
 
     def _getCssText(self):
         """Return serialized property cssText."""
diff --git a/cssutils/css/cssvalue.py b/cssutils/css/cssvalue.py
index 6a50ac6b..23d17122 100644
--- a/cssutils/css/cssvalue.py
+++ b/cssutils/css/cssvalue.py
@@ -560,12 +560,7 @@ def __init__(self, cssText=None, parent=None, readonly=False):
 
     def __str__(self):
         return (
-            "<cssutils.css.{} object primitiveType={} cssText={!r} at 0x{:x}>".format(
-                self.__class__.__name__,
-                self.primitiveTypeString,
-                self.cssText,
-                id(self),
-            )
+            f"<cssutils.css.{self.__class__.__name__} object primitiveType={self.primitiveTypeString} cssText={self.cssText!r} at 0x{id(self):x}>"
         )
 
     _unitnames = [
@@ -1136,12 +1131,7 @@ def __repr__(self):
         return f"cssutils.css.{self.__class__.__name__}({self.cssText!r})"
 
     def __str__(self):
-        return "<cssutils.css.{} object colorType={!r} cssText={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.colorType,
-            self.cssText,
-            id(self),
-        )
+        return f"<cssutils.css.{self.__class__.__name__} object colorType={self.colorType!r} cssText={self.cssText!r} at 0x{id(self):x}>"
 
     def _setCssText(self, cssText):
         self._checkReadonly()
@@ -1317,12 +1307,7 @@ def __repr__(self):
         return f"cssutils.css.{self.__class__.__name__}({self.cssText!r})"
 
     def __str__(self):
-        return "<cssutils.css.{} object name={!r} value={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.name,
-            self.value,
-            id(self),
-        )
+        return f"<cssutils.css.{self.__class__.__name__} object name={self.name!r} value={self.value!r} at 0x{id(self):x}>"
 
     def _setCssText(self, cssText):
         self._checkReadonly()
diff --git a/cssutils/css/cssvariablesdeclaration.py b/cssutils/css/cssvariablesdeclaration.py
index 7c022986..0543262a 100644
--- a/cssutils/css/cssvariablesdeclaration.py
+++ b/cssutils/css/cssvariablesdeclaration.py
@@ -49,16 +49,10 @@ def __init__(self, cssText='', parentRule=None, readonly=False):
         self._readonly = readonly
 
     def __repr__(self):
-        return "cssutils.css.{}(cssText={!r})".format(
-            self.__class__.__name__, self.cssText
-        )
+        return f"cssutils.css.{self.__class__.__name__}(cssText={self.cssText!r})"
 
     def __str__(self):
-        return "<cssutils.css.{} object length={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.length,
-            id(self),
-        )
+        return f"<cssutils.css.{self.__class__.__name__} object length={self.length!r} at 0x{id(self):x}>"
 
     def __contains__(self, variableName):
         """Check if a variable is in variable declaration block.
diff --git a/cssutils/css/cssvariablesrule.py b/cssutils/css/cssvariablesrule.py
index 34735e2f..5fe66f06 100644
--- a/cssutils/css/cssvariablesrule.py
+++ b/cssutils/css/cssvariablesrule.py
@@ -67,11 +67,7 @@ def __init__(
         self._readonly = readonly
 
     def __repr__(self):
-        return "cssutils.css.{}(mediaText={!r}, variables={!r})".format(
-            self.__class__.__name__,
-            self._media.mediaText,
-            self.variables.cssText,
-        )
+        return f"cssutils.css.{self.__class__.__name__}(mediaText={self._media.mediaText!r}, variables={self.variables.cssText!r})"
 
     def __str__(self):
         return (
diff --git a/cssutils/css/marginrule.py b/cssutils/css/marginrule.py
index 0d88067a..d486a247 100644
--- a/cssutils/css/marginrule.py
+++ b/cssutils/css/marginrule.py
@@ -100,9 +100,7 @@ def _setMargin(self, margin):
 
         if n not in MarginRule.margins:
             self._log.error(
-                'Invalid margin @keyword for this {} rule: {!r}'.format(
-                    self.margin, margin
-                ),
+                f'Invalid margin @keyword for this {self.margin} rule: {margin!r}',
                 error=xml.dom.InvalidModificationErr,
             )
 
@@ -121,11 +119,7 @@ def _setMargin(self, margin):
     atkeyword = margin
 
     def __repr__(self):
-        return "cssutils.css.{}(margin={!r}, style={!r})".format(
-            self.__class__.__name__,
-            self.margin,
-            self.style.cssText,
-        )
+        return f"cssutils.css.{self.__class__.__name__}(margin={self.margin!r}, style={self.style.cssText!r})"
 
     def __str__(self):
         return "<cssutils.css.%s object margin=%r style=%r " "at 0x%x>" % (
diff --git a/cssutils/css/property.py b/cssutils/css/property.py
index fbaf107b..7408506e 100644
--- a/cssutils/css/property.py
+++ b/cssutils/css/property.py
@@ -80,23 +80,10 @@ def __init__(
             self.priority = priority
 
     def __repr__(self):
-        return "cssutils.css.{}(name={!r}, value={!r}, priority={!r})".format(
-            self.__class__.__name__,
-            self.literalname,
-            self.propertyValue.cssText,
-            self.priority,
-        )
+        return f"cssutils.css.{self.__class__.__name__}(name={self.literalname!r}, value={self.propertyValue.cssText!r}, priority={self.priority!r})"
 
     def __str__(self):
-        return "<{}.{} object name={!r} value={!r} priority={!r} valid={!r} at 0x{:x}>".format(
-            self.__class__.__module__,
-            self.__class__.__name__,
-            self.name,
-            self.propertyValue.cssText,
-            self.priority,
-            self.valid,
-            id(self),
-        )
+        return f"<{self.__class__.__module__}.{self.__class__.__name__} object name={self.name!r} value={self.propertyValue.cssText!r} priority={self.priority!r} valid={self.valid!r} at 0x{id(self):x}>"
 
     def _isValidating(self):
         """Return True if validation is enabled."""
diff --git a/cssutils/css/value.py b/cssutils/css/value.py
index 793184a6..9fa90e64 100644
--- a/cssutils/css/value.py
+++ b/cssutils/css/value.py
@@ -259,13 +259,7 @@ def __repr__(self):
 
     def __str__(self):
         return (
-            "<cssutils.css.{} object type={} value={!r} cssText={!r} at 0x{:x}>".format(
-                self.__class__.__name__,
-                self.type,
-                self.value,
-                self.cssText,
-                id(self),
-            )
+            f"<cssutils.css.{self.__class__.__name__} object type={self.type} value={self.value!r} cssText={self.cssText!r} at 0x{id(self):x}>"
         )
 
     def _setCssText(self, cssText):
@@ -610,14 +604,7 @@ class URIValue(Value):
     _uri = Value._value
 
     def __str__(self):
-        return "<cssutils.css.{} object type={} value={!r} uri={!r} cssText={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.type,
-            self.value,
-            self.uri,
-            self.cssText,
-            id(self),
-        )
+        return f"<cssutils.css.{self.__class__.__name__} object type={self.type} value={self.value!r} uri={self.uri!r} cssText={self.cssText!r} at 0x{id(self):x}>"
 
     def _setCssText(self, cssText):
         self._checkReadonly()
@@ -794,9 +781,7 @@ class CSSCalc(CSSFunction):
     _functionName = 'CSSCalc'
 
     def __str__(self):
-        return "<cssutils.css.{} object at 0x{:x}>".format(
-            self.__class__.__name__, id(self)
-        )
+        return f"<cssutils.css.{self.__class__.__name__} object at 0x{id(self):x}>"
 
     def _setCssText(self, cssText):
         self._checkReadonly()
@@ -877,12 +862,7 @@ class CSSVariable(CSSFunction):
     _fallback = None
 
     def __str__(self):
-        return "<cssutils.css.{} object name={!r} value={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.name,
-            self.value,
-            id(self),
-        )
+        return f"<cssutils.css.{self.__class__.__name__} object name={self.name!r} value={self.value!r} at 0x{id(self):x}>"
 
     def _setCssText(self, cssText):
         self._checkReadonly()
diff --git a/cssutils/prodparser.py b/cssutils/prodparser.py
index 8ef3538b..bf1961f2 100644
--- a/cssutils/prodparser.py
+++ b/cssutils/prodparser.py
@@ -119,12 +119,7 @@ def nextProd(self, token):
             raise Exhausted('Extra token')
 
     def __repr__(self):
-        return "<cssutils.prodsparser.{} object sequence={!r} optional={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.__str__(),
-            self.optional,
-            id(self),
-        )
+        return f"<cssutils.prodsparser.{self.__class__.__name__} object sequence={self.__str__()!r} optional={self.optional!r} at 0x{id(self):x}>"
 
     def __str__(self):
         return 'Choice(%s)' % ', '.join([str(x) for x in self._prods])
@@ -239,12 +234,7 @@ def nextProd(self, token):
             raise Exhausted('Extra token')
 
     def __repr__(self):
-        return "<cssutils.prodsparser.{} object sequence={!r} optional={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.__str__(),
-            self.optional,
-            id(self),
-        )
+        return f"<cssutils.prodsparser.{self.__class__.__name__} object sequence={self.__str__()!r} optional={self.optional!r} at 0x{id(self):x}>"
 
     def __str__(self):
         return 'Sequence(%s)' % ', '.join([str(x) for x in self._prods])
@@ -359,11 +349,7 @@ def __str__(self):
         return self._name
 
     def __repr__(self):
-        return "<cssutils.prodsparser.{} object name={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self._name,
-            id(self),
-        )
+        return f"<cssutils.prodsparser.{self.__class__.__name__} object name={self._name!r} at 0x{id(self):x}>"
 
 
 # global tokenizer as there is only one!
diff --git a/cssutils/stylesheets/medialist.py b/cssutils/stylesheets/medialist.py
index 854f73c5..355e8338 100644
--- a/cssutils/stylesheets/medialist.py
+++ b/cssutils/stylesheets/medialist.py
@@ -54,17 +54,10 @@ def __init__(self, mediaText=None, parentRule=None, readonly=False):
         self._readonly = readonly
 
     def __repr__(self):
-        return "cssutils.stylesheets.{}(mediaText={!r})".format(
-            self.__class__.__name__,
-            self.mediaText,
-        )
+        return f"cssutils.stylesheets.{self.__class__.__name__}(mediaText={self.mediaText!r})"
 
     def __str__(self):
-        return "<cssutils.stylesheets.{} object mediaText={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.mediaText,
-            id(self),
-        )
+        return f"<cssutils.stylesheets.{self.__class__.__name__} object mediaText={self.mediaText!r} at 0x{id(self):x}>"
 
     def __iter__(self):
         for item in self._seq:
diff --git a/cssutils/stylesheets/mediaquery.py b/cssutils/stylesheets/mediaquery.py
index 5fd99de1..8ccb231a 100644
--- a/cssutils/stylesheets/mediaquery.py
+++ b/cssutils/stylesheets/mediaquery.py
@@ -67,17 +67,10 @@ def __init__(self, mediaText=None, readonly=False, _partof=False):
         self._readonly = readonly
 
     def __repr__(self):
-        return "cssutils.stylesheets.{}(mediaText={!r})".format(
-            self.__class__.__name__,
-            self.mediaText,
-        )
+        return f"cssutils.stylesheets.{self.__class__.__name__}(mediaText={self.mediaText!r})"
 
     def __str__(self):
-        return "<cssutils.stylesheets.{} object mediaText={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.mediaText,
-            id(self),
-        )
+        return f"<cssutils.stylesheets.{self.__class__.__name__} object mediaText={self.mediaText!r} at 0x{id(self):x}>"
 
     def _getMediaText(self):
         return cssutils.ser.do_stylesheets_mediaquery(self)
diff --git a/cssutils/tests/test_codec.py b/cssutils/tests/test_codec.py
index bf00958a..8fffbd0f 100644
--- a/cssutils/tests/test_codec.py
+++ b/cssutils/tests/test_codec.py
@@ -73,16 +73,16 @@ def test_detectencoding_str(self):
             "utf-32",
             True,
         )
-        assert codec.detectencoding_str('\x00'.encode()) == (None, False)
-        assert codec.detectencoding_str('\x00\x33'.encode()) == ("utf-8", False)
-        assert codec.detectencoding_str('\x00\x00'.encode()) == (None, False)
-        assert codec.detectencoding_str('\x00\x00\x33'.encode()) == ("utf-8", False)
+        assert codec.detectencoding_str(b'\x00') == (None, False)
+        assert codec.detectencoding_str(b'\x00\x33') == ("utf-8", False)
+        assert codec.detectencoding_str(b'\x00\x00') == (None, False)
+        assert codec.detectencoding_str(b'\x00\x00\x33') == ("utf-8", False)
         assert codec.detectencoding_str(b'\x00\x00\xfe') == (
             None,
             False,
         )
-        assert codec.detectencoding_str('\x00\x00\x00\x33'.encode()) == ("utf-8", False)
-        assert codec.detectencoding_str('\x00\x00\x00@'.encode()) == (
+        assert codec.detectencoding_str(b'\x00\x00\x00\x33') == ("utf-8", False)
+        assert codec.detectencoding_str(b'\x00\x00\x00@') == (
             "utf-32-be",
             False,
         )
@@ -91,12 +91,12 @@ def test_detectencoding_str(self):
             True,
         )
         assert codec.detectencoding_str(b'@') == (None, False)
-        assert codec.detectencoding_str('@\x33'.encode()) == ("utf-8", False)
-        assert codec.detectencoding_str('@\x00'.encode()) == (None, False)
-        assert codec.detectencoding_str('@\x00\x33'.encode()) == ("utf-8", False)
-        assert codec.detectencoding_str('@\x00\x00'.encode()) == (None, False)
-        assert codec.detectencoding_str('@\x00\x00\x33'.encode()) == ("utf-8", False)
-        assert codec.detectencoding_str('@\x00\x00\x00'.encode()) == (
+        assert codec.detectencoding_str(b'@\x33') == ("utf-8", False)
+        assert codec.detectencoding_str(b'@\x00') == (None, False)
+        assert codec.detectencoding_str(b'@\x00\x33') == ("utf-8", False)
+        assert codec.detectencoding_str(b'@\x00\x00') == (None, False)
+        assert codec.detectencoding_str(b'@\x00\x00\x33') == ("utf-8", False)
+        assert codec.detectencoding_str(b'@\x00\x00\x00') == (
             "utf-32-le",
             False,
         )
diff --git a/cssutils/tests/test_parse.py b/cssutils/tests/test_parse.py
index 08b7f6d6..e007027a 100644
--- a/cssutils/tests/test_parse.py
+++ b/cssutils/tests/test_parse.py
@@ -423,9 +423,9 @@ def test_escapes(self):
         sheet = cssutils.parseString(css)
         assert (
             sheet.cssText
-            == r'''C\x {
+            == br'''C\x {
     c\x: C\x !important
-    }'''.encode()
+    }'''
         )
 
         css = r'\ x{\ x :\ x ;y:1} '
diff --git a/cssutils/util.py b/cssutils/util.py
index 251f8c71..fbbd2998 100644
--- a/cssutils/util.py
+++ b/cssutils/util.py
@@ -593,14 +593,7 @@ def __str__(self):
             else:
                 vals.append(repr(v))
 
-        return "<cssutils.{}.{} object length={!r} items={!r} readonly={!r} at 0x{:x}>".format(
-            self.__module__,
-            self.__class__.__name__,
-            len(self),
-            vals,
-            self._readonly,
-            id(self),
-        )
+        return f"<cssutils.{self.__module__}.{self.__class__.__name__} object length={len(self)!r} items={vals!r} readonly={self._readonly!r} at 0x{id(self):x}>"
 
     def __delitem__(self, i):
         del self._seq[i]
@@ -696,14 +689,7 @@ def __init__(self, value, type, line=None, col=None):
     col = property(lambda self: self.__col)
 
     def __repr__(self):
-        return "{}.{}(value={!r}, type={!r}, line={!r}, col={!r})".format(
-            self.__module__,
-            self.__class__.__name__,
-            self.__value,
-            self.__type,
-            self.__line,
-            self.__col,
-        )
+        return f"{self.__module__}.{self.__class__.__name__}(value={self.__value!r}, type={self.__type!r}, line={self.__line!r}, col={self.__col!r})"
 
 
 class ListSeq:
@@ -872,11 +858,7 @@ def prefixForNamespaceURI(self, namespaceURI):
         raise IndexError('NamespaceURI %s not found.' % namespaceURI)
 
     def __str__(self):
-        return "<cssutils.util.{} object parentStyleSheet={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            str(self.parentStyleSheet),
-            id(self),
-        )
+        return f"<cssutils.util.{self.__class__.__name__} object parentStyleSheet={str(self.parentStyleSheet)!r} at 0x{id(self):x}>"
 
 
 class _SimpleNamespaces(_Namespaces):
@@ -899,11 +881,7 @@ def namespaces(self):
         return self.__namespaces
 
     def __str__(self):
-        return "<cssutils.util.{} object namespaces={!r} at 0x{:x}>".format(
-            self.__class__.__name__,
-            self.namespaces,
-            id(self),
-        )
+        return f"<cssutils.util.{self.__class__.__name__} object namespaces={self.namespaces!r} at 0x{id(self):x}>"
 
     def __repr__(self):
         return f"cssutils.util.{self.__class__.__name__}({self.namespaces!r})"
diff --git a/encutils/__init__.py b/encutils/__init__.py
index 8953c0bf..77226c7a 100644
--- a/encutils/__init__.py
+++ b/encutils/__init__.py
@@ -142,13 +142,7 @@ def __str__(self):
             return ''
 
     def __repr__(self):
-        return "<{}.{} object encoding={!r} mismatch={} at 0x{:x}>".format(
-            self.__class__.__module__,
-            self.__class__.__name__,
-            self.encoding,
-            self.mismatch,
-            id(self),
-        )
+        return f"<{self.__class__.__module__}.{self.__class__.__name__} object encoding={self.encoding!r} mismatch={self.mismatch} at 0x{id(self):x}>"
 
 
 def buildlog(
diff --git a/tools/try.py b/tools/try.py
index 0b4b3b17..02b6f864 100644
--- a/tools/try.py
+++ b/tools/try.py
@@ -740,9 +740,7 @@ def f(url):
                 if vi.cssValueType == vi.CSS_VARIABLE:
                     if vi.value:
                         print(
-                            '+ CSSValueList: Replacing {!r} with {!r}'.format(
-                                p.value, vi.value
-                            )
+                            f'+ CSSValueList: Replacing {p.value!r} with {vi.value!r}'
                         )
                         newvalue.append(vi.value)
                     else: