style: convert more string formatting to f-strings

22 files changed, 40 insertions, 42 deletions

diff --git a/coverage/disposition.py b/coverage/disposition.py
index 1c39a9c1..30b31af6 100644
--- a/coverage/disposition.py
+++ b/coverage/disposition.py
@@ -33,7 +33,7 @@ def disposition_debug_msg(disp):
         if disp.original_filename != disp.source_filename:
             msg += f" as {disp.source_filename!r}"
         if disp.file_tracer:
-            msg += ": will be traced by %r" % disp.file_tracer
+            msg += f": will be traced by {disp.file_tracer!r}"
     else:
         msg = f"Not tracing {disp.original_filename!r}: {disp.reason}"
     return msg
diff --git a/coverage/execfile.py b/coverage/execfile.py
index 3da3ba1f..38dc1d07 100644
--- a/coverage/execfile.py
+++ b/coverage/execfile.py
@@ -144,7 +144,7 @@ class PyRunner:
                     self.arg0 = try_filename
                     break
             else:
-                raise NoSource("Can't find '__main__' module in '%s'" % self.arg0)
+                raise NoSource(f"Can't find '__main__' module in '{self.arg0}'")
 
             # Make a spec. I don't know if this is the right way to do it.
             try_filename = python_reported_file(try_filename)
diff --git a/coverage/misc.py b/coverage/misc.py
index 584efeaa..fa09f890 100644
--- a/coverage/misc.py
+++ b/coverage/misc.py
@@ -184,7 +184,7 @@ def bool_or_none(b):
 
 def join_regex(regexes):
     """Combine a list of regexes into one that matches any of them."""
-    return "|".join("(?:%s)" % r for r in regexes)
+    return "|".join(f"(?:{r})" for r in regexes)
 
 
 def file_be_gone(path):
diff --git a/coverage/results.py b/coverage/results.py
index 11c4b09b..64e5130c 100644
--- a/coverage/results.py
+++ b/coverage/results.py
@@ -317,7 +317,7 @@ def format_lines(statements, lines, arcs=None):
             for ex in sorted(exits):
                 if line not in lines and ex not in lines:
                     dest = (ex if ex > 0 else "exit")
-                    line_items.append((line, "%d->%s" % (line, dest)))
+                    line_items.append((line, f"{line}->{dest}"))
 
     ret = ', '.join(t[-1] for t in sorted(line_items))
     return ret
diff --git a/coverage/version.py b/coverage/version.py
index 41244144..394cd076 100644
--- a/coverage/version.py
+++ b/coverage/version.py
@@ -16,7 +16,7 @@ def _make_version(major, minor, micro, releaselevel, serial):
         version += ".%d" % (micro,)
     if releaselevel != 'final':
         short = {'alpha': 'a', 'beta': 'b', 'candidate': 'rc'}[releaselevel]
-        version += "%s%d" % (short, serial)
+        version += f"{short}{serial}"
     return version
 
 
diff --git a/coverage/xmlreport.py b/coverage/xmlreport.py
index 8c8409dc..ebc85de4 100644
--- a/coverage/xmlreport.py
+++ b/coverage/xmlreport.py
@@ -67,9 +67,9 @@ class XmlReporter:
         xcoverage.setAttribute("version", __version__)
         xcoverage.setAttribute("timestamp", str(int(time.time()*1000)))
         xcoverage.appendChild(self.xml_out.createComment(
-            " Generated by coverage.py: %s " % __url__
+            f" Generated by coverage.py: {__url__} "
             ))
-        xcoverage.appendChild(self.xml_out.createComment(" Based on %s " % DTD_URL))
+        xcoverage.appendChild(self.xml_out.createComment(f" Based on {DTD_URL} "))
 
         # Call xml_file for each file in the data.
         for fr, analysis in get_analysis_to_report(self.coverage, morfs):
diff --git a/igor.py b/igor.py
index 12e63f09..05788148 100644
--- a/igor.py
+++ b/igor.py
@@ -282,14 +282,14 @@ def do_check_eol():
             for n, line in enumerate(f, start=1):
                 if crlf:
                     if b"\r" in line:
-                        print("%s@%d: CR found" % (fname, n))
+                        print(f"{fname}@{n}: CR found")
                         return
                 if trail_white:
                     line = line[:-1]
                     if not crlf:
                         line = line.rstrip(b'\r')
                     if line.rstrip() != line:
-                        print("%s@%d: trailing whitespace found" % (fname, n))
+                        print(f"{fname}@{n}: trailing whitespace found")
                         return
 
         if line is not None and not line.strip():
@@ -391,7 +391,7 @@ def main(args):
         verb = args.pop(0)
         handler = globals().get('do_'+verb)
         if handler is None:
-            print("*** No handler for %r" % verb)
+            print(f"*** No handler for {verb!r}")
             return 1
         star, num_args = analyze_args(handler)
         if star:
diff --git a/tests/coveragetest.py b/tests/coveragetest.py
index 0960722b..52b0a6ab 100644
--- a/tests/coveragetest.py
+++ b/tests/coveragetest.py
@@ -275,13 +275,11 @@ class CoverageTest(
 
     def assert_exists(self, fname):
         """Assert that `fname` is a file that exists."""
-        msg = "File %r should exist" % fname
-        assert os.path.exists(fname), msg
+        assert os.path.exists(fname), f"File {fname!r} should exist"
 
     def assert_doesnt_exist(self, fname):
         """Assert that `fname` is a file that doesn't exist."""
-        msg = "File %r shouldn't exist" % fname
-        assert not os.path.exists(fname), msg
+        assert not os.path.exists(fname), f"File {fname!r} shouldn't exist"
 
     def assert_file_count(self, pattern, count):
         """Assert that there are `count` files matching `pattern`."""
diff --git a/tests/gold/annotate/anno_dir/d_b039179a8a4ce2c2_b.py,cover b/tests/gold/annotate/anno_dir/d_b039179a8a4ce2c2_b.py,cover
index 90d076f1..382f1901 100644
--- a/tests/gold/annotate/anno_dir/d_b039179a8a4ce2c2_b.py,cover
+++ b/tests/gold/annotate/anno_dir/d_b039179a8a4ce2c2_b.py,cover
@@ -1,3 +1,3 @@
 > def b(x):
->     msg = "x is %s" % x
+>     msg = f"x is {x}"
 >     print(msg)
diff --git a/tests/modules/process_test/try_execfile.py b/tests/modules/process_test/try_execfile.py
index 48f9d098..2c741662 100644
--- a/tests/modules/process_test/try_execfile.py
+++ b/tests/modules/process_test/try_execfile.py
@@ -61,7 +61,7 @@ import __main__
 
 def my_function(a):
     """A function to force execution of module-level values."""
-    return "my_fn(%r)" % a
+    return f"my_fn({a!r})"
 
 FN_VAL = my_function("fooey")
 
diff --git a/tests/test_annotate.py b/tests/test_annotate.py
index 97f2080b..09893143 100644
--- a/tests/test_annotate.py
+++ b/tests/test_annotate.py
@@ -32,7 +32,7 @@ class AnnotationGoldTest(CoverageTest):
         self.make_file("b/__init__.py")
         self.make_file("b/b.py", """\
             def b(x):
-                msg = "x is %s" % x
+                msg = f"x is {x}"
                 print(msg)
             """)
 
diff --git a/tests/test_arcs.py b/tests/test_arcs.py
index 349a560f..817943e9 100644
--- a/tests/test_arcs.py
+++ b/tests/test_arcs.py
@@ -1835,7 +1835,7 @@ class AsyncTest(CoverageTest):
             import asyncio
 
             async def compute(x, y):                        # 3
-                print("Compute %s + %s ..." % (x, y))
+                print(f"Compute {x} + {y} ...")
                 await asyncio.sleep(0.001)
                 return x + y                                # 6
 
@@ -1843,7 +1843,7 @@ class AsyncTest(CoverageTest):
                 result = (0 +
                             await compute(x, y)             # A
                 )
-                print("%s + %s = %s" % (x, y, result))
+                print(f"{x} + {y} = {result}")
 
             loop = asyncio.new_event_loop()                 # E
             loop.run_until_complete(print_sum(1, 2))
diff --git a/tests/test_concurrency.py b/tests/test_concurrency.py
index c39b0163..6db75e69 100644
--- a/tests/test_concurrency.py
+++ b/tests/test_concurrency.py
@@ -215,7 +215,7 @@ class ConcurrencyTest(CoverageTest):
 
         self.make_file("try_it.py", code)
 
-        cmd = "coverage run --concurrency=%s try_it.py" % concurrency
+        cmd = f"coverage run --concurrency={concurrency} try_it.py"
         out = self.run_command(cmd)
 
         expected_cant_trace = cant_trace_msg(concurrency, the_module)
@@ -366,11 +366,11 @@ class MultiprocessingTest(CoverageTest):
     ):
         """Run code using multiprocessing, it should produce `expected_out`."""
         self.make_file("multi.py", code)
-        self.make_file(".coveragerc", """\
+        self.make_file(".coveragerc", f"""\
             [run]
-            concurrency = %s
+            concurrency = {concurrency}
             source = .
-            """ % concurrency)
+            """)
 
         for start_method in ["fork", "spawn"]:
             if start_method and start_method not in multiprocessing.get_all_start_methods():
diff --git a/tests/test_config.py b/tests/test_config.py
index c2874188..ad3b446a 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -181,7 +181,7 @@ class ConfigTest(CoverageTest):
         ]
 
         for bad_config, msg in bad_configs_and_msgs:
-            print("Trying %r" % bad_config)
+            print(f"Trying {bad_config!r}")
             self.make_file(".coveragerc", bad_config)
             with pytest.raises(CoverageException, match=msg):
                 coverage.Coverage()
@@ -689,7 +689,7 @@ class ConfigFileTest(UsingModulesMixin, CoverageTest):
             ".",
         ]
         for bad_file in bad_files:
-            msg = "Couldn't read %r as a config file" % bad_file
+            msg = f"Couldn't read {bad_file!r} as a config file"
             with pytest.raises(CoverageException, match=msg):
                 coverage.Coverage(config_file=bad_file)
 
diff --git a/tests/test_debug.py b/tests/test_debug.py
index 1ea72e82..42f41706 100644
--- a/tests/test_debug.py
+++ b/tests/test_debug.py
@@ -171,8 +171,8 @@ class DebugTraceTest(CoverageTest):
             report_include report_omit
             """.split()
         for label in labels:
-            label_pat = r"^\s*%s: " % label
-            msg = "Incorrect lines for %r" % label
+            label_pat = fr"^\s*{label}: "
+            msg = f"Incorrect lines for {label!r}"
             assert 1 == len(re_lines(label_pat, out_lines)), msg
 
     def test_debug_sys(self):
@@ -185,8 +185,8 @@ class DebugTraceTest(CoverageTest):
             pid cwd path environment command_line cover_match pylib_match
             """.split()
         for label in labels:
-            label_pat = r"^\s*%s: " % label
-            msg = "Incorrect lines for %r" % label
+            label_pat = fr"^\s*{label}: "
+            msg = f"Incorrect lines for {label!r}"
             assert 1 == len(re_lines(label_pat, out_lines)), msg
 
     def test_debug_sys_ctracer(self):
diff --git a/tests/test_execfile.py b/tests/test_execfile.py
index b7a09902..d211eba9 100644
--- a/tests/test_execfile.py
+++ b/tests/test_execfile.py
@@ -83,7 +83,7 @@ class RunFileTest(CoverageTest):
         self.make_file("abrupt.py", """\
             if 1:
                 a = 1
-                print("a is %r" % a)
+                print(f"a is {a!r}")
                 #""")
         with open("abrupt.py") as f:
             abrupt = f.read()
diff --git a/tests/test_oddball.py b/tests/test_oddball.py
index 19c93be5..2eb0fc1d 100644
--- a/tests/test_oddball.py
+++ b/tests/test_oddball.py
@@ -475,7 +475,7 @@ class GettraceTest(CoverageTest):
 
             def tracer(frame, event, arg):
                 filename = os.path.basename(frame.f_code.co_filename)
-                print("%s: %s @ %d" % (event, filename, frame.f_lineno))
+                print(f"{event}: {filename} @ {frame.f_lineno}")
                 return tracer
 
             def begin():
diff --git a/tests/test_parser.py b/tests/test_parser.py
index 538e2500..6dcfc00a 100644
--- a/tests/test_parser.py
+++ b/tests/test_parser.py
@@ -463,7 +463,7 @@ class ParserFileTest(CoverageTest):
             fname = fname + ".py"
             self.make_file(fname, text, newline=newline)
             parser = self.parse_file(fname)
-            assert parser.exit_counts() == counts, "Wrong for %r" % fname
+            assert parser.exit_counts() == counts, f"Wrong for {fname!r}"
 
     def test_encoding(self):
         self.make_file("encoded.py", """\
diff --git a/tests/test_phystokens.py b/tests/test_phystokens.py
index 9950e655..91a9d3d9 100644
--- a/tests/test_phystokens.py
+++ b/tests/test_phystokens.py
@@ -171,7 +171,7 @@ class SourceEncodingTest(CoverageTest):
 
     def test_detect_source_encoding(self):
         for _, source, expected in ENCODING_DECLARATION_SOURCES:
-            assert source_encoding(source) == expected, "Wrong encoding in %r" % source
+            assert source_encoding(source) == expected, f"Wrong encoding in {source!r}"
 
     # PyPy3 gets this case wrong. Not sure what I can do about it, so skip the test.
     @pytest.mark.skipif(env.PYPY, reason="PyPy3 is wrong about non-comment encoding. Skip it.")
@@ -233,7 +233,7 @@ class NeuterEncodingDeclarationTest(CoverageTest):
 
             # The neutered source will be detected as having no encoding
             # declaration.
-            assert source_encoding(neutered) == DEF_ENCODING, "Wrong encoding in %r" % neutered
+            assert source_encoding(neutered) == DEF_ENCODING, f"Wrong encoding in {neutered!r}"
 
     def test_two_encoding_declarations(self):
         input_src = textwrap.dedent("""\
diff --git a/tests/test_plugins.py b/tests/test_plugins.py
index 17c7ba44..5d3b5322 100644
--- a/tests/test_plugins.py
+++ b/tests/test_plugins.py
@@ -988,7 +988,7 @@ class DynamicContextPluginTest(CoverageTest):
         """Make some files to use while testing dynamic context plugins."""
         self.make_file("rendering.py", """\
             def html_tag(tag, content):
-                return '<%s>%s</%s>' % (tag, content, tag)
+                return f'<{tag}>{content}</{tag}>'
 
             def render_paragraph(text):
                 return html_tag('p', text)
diff --git a/tests/test_process.py b/tests/test_process.py
index 83ca1feb..58f32707 100644
--- a/tests/test_process.py
+++ b/tests/test_process.py
@@ -382,7 +382,7 @@ class ProcessTest(CoverageTest):
         self.make_file("d1/x.py", """\
             a = 1
             b = 2
-            print("%s %s" % (a, b))
+            print(f"{a} {b}")
             """)
 
         self.make_file("d2/x.py", """\
@@ -391,7 +391,7 @@ class ProcessTest(CoverageTest):
             # 3
             c = 4
             d = 5
-            print("%s %s" % (c, d))
+            print(f"{c} {d}")
             """)
 
         self.make_file(".coveragerc", """\
@@ -823,7 +823,7 @@ class ProcessTest(CoverageTest):
             import coverage
 
             for i in [1, 2]:
-                sys.stderr.write("Run %s\\n" % i)
+                sys.stderr.write(f"Run {i}\\n")
                 inst = coverage.Coverage(source=['foo'])
                 inst.load()
                 inst.start()
@@ -1206,9 +1206,9 @@ class AliasedCommandTest(CoverageTest):
             "coverage-%d.%d" % sys.version_info[:2],
         ]
         for cmd in cmds:
-            out = self.run_command("%s foobar" % cmd)
+            out = self.run_command(f"{cmd} foobar")
             assert "Unknown command: 'foobar'" in out
-            assert "Use '%s help' for help" % cmd in out
+            assert f"Use '{cmd} help' for help" in out
 
 
 class PydocTest(CoverageTest):
@@ -1557,7 +1557,7 @@ class ProcessStartupTest(ProcessCoverageMixin, CoverageTest):
         data_files = glob.glob(os.getcwd() + '/.coverage*')
         msg = (
             "Expected only .coverage after combine, looks like there are " +
-            "extra data files that were not cleaned up: %r" % data_files
+            f"extra data files that were not cleaned up: {data_files!r}"
         )
         assert len(data_files) == 1, msg
 
diff --git a/tests/test_summary.py b/tests/test_summary.py
index 03660542..6fbb034d 100644
--- a/tests/test_summary.py
+++ b/tests/test_summary.py
@@ -631,7 +631,7 @@ class SummaryTest(UsingModulesMixin, CoverageTest):
             if not b:
                 c = 6
             d = 7
-            print("xxx: %r %r %r %r" % (a, b, c, d))
+            print(f"xxx: {a} {b} {c} {d}")
             """)
         out = self.run_command("coverage run --source=. xxx")
         assert out == "xxx: 3 4 0 7\n"