Migrate from % syntax or bad format() syntax to fstring

We can do that in python 3.6

15 files changed, 62 insertions, 127 deletions

diff --git a/pylint/checkers/base.py b/pylint/checkers/base.py
index 647c201d9..0a836de4c 100644
--- a/pylint/checkers/base.py
+++ b/pylint/checkers/base.py
@@ -1331,7 +1331,6 @@ class BasicChecker(_BasicChecker):
                 isinstance(value, astroid.Instance)
                 and value.qname() in DEFAULT_ARGUMENT_SYMBOLS
             ):
-
                 if value is default:
                     msg = DEFAULT_ARGUMENT_SYMBOLS[value.qname()]
                 elif isinstance(value, astroid.Instance) or is_iterable(value):
@@ -1350,10 +1349,7 @@ class BasicChecker(_BasicChecker):
                         msg = f"{default.as_string()} ({value.qname()})"
                 else:
                     # this argument is a name
-                    msg = "{} ({})".format(
-                        default.as_string(),
-                        DEFAULT_ARGUMENT_SYMBOLS[value.qname()],
-                    )
+                    msg = f"{default.as_string()} ({DEFAULT_ARGUMENT_SYMBOLS[value.qname()]})"
                 self.add_message("dangerous-default-value", node=node, args=(msg,))
 
     @utils.check_messages("unreachable", "lost-exception")
@@ -2437,14 +2433,9 @@ class ComparisonChecker(_BasicChecker):
         if checking_for_absence:
             absence_text = "not "
         if nan_left:
-            suggestion = "'{}math.isnan({})'".format(
-                absence_text, right_value.as_string()
-            )
+            suggestion = f"'{absence_text}math.isnan({right_value.as_string()})'"
         else:
-            suggestion = "'{}math.isnan({})'".format(
-                absence_text, left_value.as_string()
-            )
-
+            suggestion = f"'{absence_text}math.isnan({left_value.as_string()})'"
         self.add_message(
             "nan-comparison",
             node=root_node,
diff --git a/pylint/checkers/classes.py b/pylint/checkers/classes.py
index aada6bbf3..83abf758f 100644
--- a/pylint/checkers/classes.py
+++ b/pylint/checkers/classes.py
@@ -1604,7 +1604,7 @@ a metaclass class method.",
                 valid = repr(config[0])
             else:
                 valid = ", ".join(repr(v) for v in config[:-1])
-                valid = "{} or {!r}".format(valid, config[-1])
+                valid = f"{valid} or {config[-1]!r}"
             self.add_message(message, args=(method_name, valid), node=node)
 
     def _check_bases_classes(self, node):
diff --git a/pylint/checkers/variables.py b/pylint/checkers/variables.py
index 01cf8ecbd..1e96f1b4e 100644
--- a/pylint/checkers/variables.py
+++ b/pylint/checkers/variables.py
@@ -1643,11 +1643,7 @@ class VariablesChecker(BaseChecker):
                     return
                 if isinstance(stmt, astroid.ImportFrom):
                     if asname is not None:
-                        msg = "{} imported from {} as {}".format(
-                            qname,
-                            stmt.modname,
-                            asname,
-                        )
+                        msg = f"{qname} imported from {stmt.modname} as {asname}"
                     else:
                         msg = f"{name} imported from {stmt.modname}"
                     self.add_message("unused-import", args=msg, node=stmt)
diff --git a/pylint/config/__init__.py b/pylint/config/__init__.py
index 41c303666..c893cdbea 100644
--- a/pylint/config/__init__.py
+++ b/pylint/config/__init__.py
@@ -68,7 +68,7 @@ else:
 
 def _get_pdata_path(base_name, recurs):
     base_name = base_name.replace(os.sep, "_")
-    return os.path.join(PYLINT_HOME, "{}{}{}".format(base_name, recurs, ".stats"))
+    return os.path.join(PYLINT_HOME, f"{base_name}{recurs}.stats")
 
 
 def load_results(base):
diff --git a/pylint/config/man_help_formatter.py b/pylint/config/man_help_formatter.py
index ab3b7e749..bd15e76a3 100644
--- a/pylint/config/man_help_formatter.py
+++ b/pylint/config/man_help_formatter.py
@@ -33,12 +33,9 @@ class _ManHelpFormatter(optparse.HelpFormatter):
             help_string = help_string.replace("[current:", "[default:")
         else:
             help_string = ""
-        return """.IP "{}"
-{}
-""".format(
-            optstring,
-            help_string,
-        )
+        return f""".IP "{optstring}"
+{help_string}
+"""
 
     def format_head(self, optparser, pkginfo, section=1):
         long_desc = ""
@@ -50,12 +47,10 @@ class _ManHelpFormatter(optparse.HelpFormatter):
         short_desc = self.format_short_description(pgm, pkginfo.description)
         if hasattr(pkginfo, "long_desc"):
             long_desc = self.format_long_description(pgm, pkginfo.long_desc)
-        return "{}\n{}\n{}\n{}".format(
-            self.format_title(pgm, section),
-            short_desc,
-            self.format_synopsis(pgm),
-            long_desc,
-        )
+        return f"""{self.format_title(pgm, section)}
+{short_desc}
+{self.format_synopsis(pgm)}
+{long_desc}"""
 
     @staticmethod
     def format_title(pgm, section):
@@ -64,27 +59,21 @@ class _ManHelpFormatter(optparse.HelpFormatter):
 
     @staticmethod
     def format_short_description(pgm, short_desc):
-        return """.SH NAME
-.B {}
-\\- {}
-""".format(
-            pgm,
-            short_desc.strip(),
-        )
+        return f""".SH NAME
+.B {pgm}
+\\- {short_desc.strip()}
+"""
 
     @staticmethod
     def format_synopsis(pgm):
-        return (
-            """.SH SYNOPSIS
-.B  %s
+        return f""".SH SYNOPSIS
+.B  {pgm}
 [
 .I OPTIONS
 ] [
 .I <arguments>
 ]
 """
-            % pgm
-        )
 
     @staticmethod
     def format_long_description(pgm, long_desc):
@@ -92,41 +81,28 @@ class _ManHelpFormatter(optparse.HelpFormatter):
         long_desc = long_desc.replace("\n.\n", "\n\n")
         if long_desc.lower().startswith(pgm):
             long_desc = long_desc[len(pgm) :]
-        return """.SH DESCRIPTION
-.B {}
-{}
-""".format(
-            pgm,
-            long_desc.strip(),
-        )
+        return f""".SH DESCRIPTION
+.B {pgm}
+{long_desc.strip()}
+"""
 
     @staticmethod
     def format_tail(pkginfo):
-        tail = """.SH SEE ALSO
-/usr/share/doc/pythonX.Y-{}/
+        tail = f""".SH SEE ALSO
+/usr/share/doc/pythonX.Y-{getattr(pkginfo, "debian_name", "pylint")}/
 
 .SH BUGS
 Please report bugs on the project\'s mailing list:
-{}
+{pkginfo.mailinglist}
 
 .SH AUTHOR
-{} <{}>
-""".format(
-            getattr(pkginfo, "debian_name", "pylint"),
-            pkginfo.mailinglist,
-            pkginfo.author,
-            pkginfo.author_email,
-        )
-
+{pkginfo.author} <{pkginfo.author_email}>
+"""
         if hasattr(pkginfo, "copyright"):
-            tail += (
-                """
+            tail += f"""
 .SH COPYRIGHT
-%s
+{pkginfo.copyright}
 """
-                % pkginfo.copyright
-            )
-
         return tail
 
 
diff --git a/pylint/constants.py b/pylint/constants.py
index f6f3b189b..929eed97e 100644
--- a/pylint/constants.py
+++ b/pylint/constants.py
@@ -44,8 +44,6 @@ class WarningScope:
     NODE = "node-based-msg"
 
 
-full_version = "pylint {}\nastroid {}\nPython {}".format(
-    pylint_version,
-    astroid_version,
-    sys.version,
-)
+full_version = f"""pylint {pylint_version}
+astroid {astroid_version}
+Python { sys.version}"""
diff --git a/pylint/message/message_definition.py b/pylint/message/message_definition.py
index 3fb9af945..6f5f0dc51 100644
--- a/pylint/message/message_definition.py
+++ b/pylint/message/message_definition.py
@@ -39,17 +39,15 @@ class MessageDefinition:
     @staticmethod
     def check_msgid(msgid: str) -> None:
         if len(msgid) != 5:
-            raise InvalidMessageError("Invalid message id %r" % msgid)
+            raise InvalidMessageError(f"Invalid message id {msgid!r}")
         if msgid[0] not in MSG_TYPES:
-            raise InvalidMessageError(
-                "Bad message type {} in {!r}".format(msgid[0], msgid)
-            )
+            raise InvalidMessageError(f"Bad message type {msgid[0]} in {msgid!r}")
 
     def __repr__(self):
         return f"MessageDefinition:{self.symbol} ({self.msgid})"
 
     def __str__(self):
-        return "{}:\n{} {}".format(repr(self), self.msg, self.description)
+        return f"{repr(self)}:\n{self.msg} {self.description}"
 
     def may_be_emitted(self):
         """return True if message may be emitted using the current interpreter"""
diff --git a/pylint/message/message_id_store.py b/pylint/message/message_id_store.py
index 0395f0878..438136cb5 100644
--- a/pylint/message/message_id_store.py
+++ b/pylint/message/message_id_store.py
@@ -81,9 +81,7 @@ class MessageIdStore:
         symbols = [symbol, other_symbol]
         symbols.sort()
         error_message = f"Message id '{msgid}' cannot have both "
-        error_message += "'{other_symbol}' and '{symbol}' as symbolic name.".format(
-            other_symbol=symbols[0], symbol=symbols[1]
-        )
+        error_message += f"'{symbols[0]}' and '{symbols[1]}' as symbolic name."
         raise InvalidMessageError(error_message)
 
     @staticmethod
@@ -97,10 +95,10 @@ class MessageIdStore:
         msgids = [msgid, other_msgid]
         msgids.sort()
         error_message = (
-            "Message symbol '{symbol}' cannot be used for "
-            "'{other_msgid}' and '{msgid}' at the same time."
-            " If you're creating an 'old_names' use 'old-{symbol}' as the old symbol."
-        ).format(symbol=symbol, other_msgid=msgids[0], msgid=msgids[1])
+            f"Message symbol '{symbol}' cannot be used for "
+            f"'{msgids[0]}' and '{msgids[1]}' at the same time."
+            f" If you're creating an 'old_names' use 'old-{symbol}' as the old symbol."
+        )
         raise InvalidMessageError(error_message)
 
     def get_active_msgids(self, msgid_or_symbol: str) -> List[str]:
diff --git a/pylint/pyreverse/inspector.py b/pylint/pyreverse/inspector.py
index 17ef46bff..cdae95e6b 100644
--- a/pylint/pyreverse/inspector.py
+++ b/pylint/pyreverse/inspector.py
@@ -261,7 +261,7 @@ class Linker(IdGeneratorMixIn, utils.LocalsVisitor):
             if name[0] == "*":
                 continue
             # analyze dependencies
-            fullname = "{}.{}".format(basename, name[0])
+            fullname = f"{basename}.{name[0]}"
             if fullname.find(".") > -1:
                 try:
                     fullname = modutils.get_module_part(fullname, context_file)
@@ -319,11 +319,7 @@ class Project:
         return self.modules
 
     def __repr__(self):
-        return "<Project {!r} at {} ({} modules)>".format(
-            self.name,
-            id(self),
-            len(self.modules),
-        )
+        return f"<Project {self.name!r} at {id(self)} ({len(self.modules)} modules)>"
 
 
 def project_from_files(
diff --git a/pylint/pyreverse/vcgutils.py b/pylint/pyreverse/vcgutils.py
index 36e82032a..3041b076e 100644
--- a/pylint/pyreverse/vcgutils.py
+++ b/pylint/pyreverse/vcgutils.py
@@ -204,14 +204,13 @@ possible attributes are %s"""
             if not _type:
                 self._stream.write(f'{self._indent}{key}:"{value}"\n')
             elif _type == 1:
-                self._stream.write("{}{}:{}\n".format(self._indent, key, int(value)))
+                self._stream.write(f"{self._indent}{key}:{int(value)}\n")
             elif value in _type:
                 self._stream.write(f"{self._indent}{key}:{value}\n")
             else:
                 raise Exception(
-                    """value %s isn\'t correct for attribute %s
-correct values are %s"""
-                    % (value, key, _type)
+                    f"""value {value} isn't correct for attribute {key}
+correct values are {type}"""
                 )
 
     def _inc_indent(self):
diff --git a/pylint/testutils/lint_module_test.py b/pylint/testutils/lint_module_test.py
index 5b9dc5c7a..c0dc4f002 100644
--- a/pylint/testutils/lint_module_test.py
+++ b/pylint/testutils/lint_module_test.py
@@ -70,11 +70,7 @@ class LintModuleTest:
         )
 
     def __str__(self):
-        return "{} ({}.{})".format(
-            self._test_file.base,
-            self.__class__.__module__,
-            self.__class__.__name__,
-        )
+        return f"{self._test_file.base} ({self.__class__.__module__}.{self.__class__.__name__})"
 
     @staticmethod
     def get_expected_messages(stream):
diff --git a/pylint/utils/utils.py b/pylint/utils/utils.py
index 0f4e0f518..981bfb91b 100644
--- a/pylint/utils/utils.py
+++ b/pylint/utils/utils.py
@@ -52,7 +52,7 @@ def get_module_and_frameid(node):
 
 def get_rst_title(title, character):
     """Permit to get a title formatted as ReStructuredText test (underlined with a chosen character)."""
-    return "{}\n{}\n".format(title, character * len(title))
+    return f"{title}\n{character * len(title)}\n"
 
 
 def get_rst_section(section, options, doc=None):
diff --git a/tests/checkers/unittest_base.py b/tests/checkers/unittest_base.py
index f8371d3ad..7534e0fbb 100644
--- a/tests/checkers/unittest_base.py
+++ b/tests/checkers/unittest_base.py
@@ -551,23 +551,17 @@ class TestNamePresets(unittest.TestCase):
         for name, name_type in always_pass_data:
             self._test_is_correct(naming_style, name, name_type)
 
-    def _test_is_correct(self, naming_style, name, name_type):
+    @staticmethod
+    def _test_is_correct(naming_style, name, name_type):
         rgx = naming_style.get_regex(name_type)
-        self.assertTrue(
-            rgx.match(name),
-            "{!r} does not match pattern {!r} (style: {}, type: {})".format(
-                name, rgx, naming_style, name_type
-            ),
-        )
+        fail = f"{name!r} does not match pattern {rgx!r} (style: {naming_style}, type: {name_type})"
+        assert rgx.match(name), fail
 
-    def _test_is_incorrect(self, naming_style, name, name_type):
+    @staticmethod
+    def _test_is_incorrect(naming_style, name, name_type):
         rgx = naming_style.get_regex(name_type)
-        self.assertFalse(
-            rgx.match(name),
-            "{!r} match pattern {!r} but shouldn't (style: {}, type: {})".format(
-                name, rgx, naming_style, name_type
-            ),
-        )
+        fail = f"{name!r} not match pattern {rgx!r} (style: {naming_style}, type: {name_type})"
+        assert not rgx.match(name), fail
 
     def test_snake_case(self):
         naming_style = base.SnakeCaseStyle
diff --git a/tests/checkers/unittest_spelling.py b/tests/checkers/unittest_spelling.py
index 80fdc3888..165199563 100644
--- a/tests/checkers/unittest_spelling.py
+++ b/tests/checkers/unittest_spelling.py
@@ -44,9 +44,8 @@ class TestSpellingChecker(CheckerTestCase):
     )
 
     def _get_msg_suggestions(self, word, count=4):
-        return "'{}'".format(
-            "' or '".join(self.checker.spelling_dict.suggest(word)[:count])
-        )
+        suggestions = "' or '".join(self.checker.spelling_dict.suggest(word)[:count])
+        return f"'{suggestions}'"
 
     @skip_on_missing_package_or_dict
     @set_config(spelling_dict=spell_dict)
diff --git a/tests/unittest_pyreverse_writer.py b/tests/unittest_pyreverse_writer.py
index 20f128574..1c2767e9a 100644
--- a/tests/unittest_pyreverse_writer.py
+++ b/tests/unittest_pyreverse_writer.py
@@ -106,12 +106,10 @@ def test_dot_files(generated_file):
     generated = "\n".join(generated)
     expected = "\n".join(expected)
     files = f"\n *** expected : {expected_file}, generated : {generated_file} \n"
-    assert expected == generated, "{}{}".format(
-        files,
-        "\n".join(
-            line for line in unified_diff(expected.splitlines(), generated.splitlines())
-        ),
+    diff = "\n".join(
+        line for line in unified_diff(expected.splitlines(), generated.splitlines())
     )
+    assert expected == generated, f"{files}{diff}"
     os.remove(generated_file)
 
 
@@ -130,8 +128,4 @@ def test_dot_files(generated_file):
 def test_get_visibility(names, expected):
     for name in names:
         got = get_visibility(name)
-        assert got == expected, "got {} instead of {} for value {}".format(
-            got,
-            expected,
-            name,
-        )
+        assert got == expected, f"got {got} instead of {expected} for value {name}"