From e2fb5c0d5e9d156c4e96d44501af6af88b658cec Mon Sep 17 00:00:00 2001
From: Steffen Rehberg <steffen.rehberg@googlemail.com>
Date: Mon, 24 Apr 2023 21:06:29 +0200
Subject: [PATCH] MNT: Change % formatting to f-strings

- change remaining old-style % formatting to f-strings
  (cases like '%s' % var or 'str1' 'str2 %s' % (var,) which are not
  handled by pyupgrade due to their potential ambiguity)
- change logging.debug("... %s ..." % x) to logging.debug("... %s ...", x)
  for uniformity
- remove some u string prefixes
---
 sphinx_gallery/backreferences.py         | 10 +--
 sphinx_gallery/directives.py             |  8 +--
 sphinx_gallery/docs_resolv.py            |  2 +-
 sphinx_gallery/gen_gallery.py            | 87 ++++++++++++------------
 sphinx_gallery/gen_rst.py                | 24 +++----
 sphinx_gallery/interactive_example.py    |  5 +-
 sphinx_gallery/notebook.py               |  5 +-
 sphinx_gallery/scrapers.py               |  9 ++-
 sphinx_gallery/tests/conftest.py         |  8 +--
 sphinx_gallery/tests/test_full.py        | 21 +++---
 sphinx_gallery/tests/test_gen_gallery.py |  2 +-
 sphinx_gallery/tests/test_gen_rst.py     |  4 +-
 sphinx_gallery/utils.py                  |  6 +-
 13 files changed, 93 insertions(+), 98 deletions(-)

diff --git a/sphinx_gallery/backreferences.py b/sphinx_gallery/backreferences.py
index ed8316bd2..2d070f54b 100644
--- a/sphinx_gallery/backreferences.py
+++ b/sphinx_gallery/backreferences.py
@@ -293,11 +293,11 @@ def _thumbnail_div(target_dir, src_dir, fname, snippet, title,
     """Generate reST to place a thumbnail in a gallery."""
     thumb, _ = _find_image_ext(
         os.path.join(target_dir, 'images', 'thumb',
-                     'sphx_glr_%s_thumb.png' % fname[:-3]))
+                     f'sphx_glr_{fname[:-3]}_thumb.png'))
     if check and not os.path.isfile(thumb):
         # This means we have done something wrong in creating our thumbnail!
         raise ExtensionError('Could not find internal Sphinx-Gallery thumbnail'
-                             ' file:\n%s' % (thumb,))
+                             f' file:\n{thumb}')
     thumb = os.path.relpath(thumb, src_dir)
     full_dir = os.path.relpath(target_dir, src_dir)
 
@@ -320,14 +320,14 @@ def _write_backreferences(backrefs, seen_backrefs, gallery_conf,
     for backref in backrefs:
         include_path = os.path.join(gallery_conf['src_dir'],
                                     gallery_conf['backreferences_dir'],
-                                    '%s.examples.new' % backref)
+                                    f'{backref}.examples.new')
         seen = backref in seen_backrefs
         with codecs.open(include_path, 'a' if seen else 'w',
                          encoding='utf-8') as ex_file:
             if not seen:
                 # Be aware that if the number of lines of this heading changes,
                 #   the minigallery directive should be modified accordingly
-                heading = 'Examples using ``%s``' % backref
+                heading = f'Examples using ``{backref}``'
                 ex_file.write('\n\n' + heading + '\n')
                 ex_file.write('^' * len(heading) + '\n')
                 ex_file.write('\n\n.. start-sphx-glr-thumbnails\n\n')
@@ -349,7 +349,7 @@ def _finalize_backreferences(seen_backrefs, gallery_conf):
     for backref in seen_backrefs:
         path = os.path.join(gallery_conf['src_dir'],
                             gallery_conf['backreferences_dir'],
-                            '%s.examples.new' % backref)
+                            f'{backref}.examples.new')
         if os.path.isfile(path):
             # Close div containing all thumbnails
             # (it was open in _write_backreferences)
diff --git a/sphinx_gallery/directives.py b/sphinx_gallery/directives.py
index 440a50d42..f12f12385 100644
--- a/sphinx_gallery/directives.py
+++ b/sphinx_gallery/directives.py
@@ -40,7 +40,7 @@ def run(self):
         # Respect the same disabling options as the `raw` directive
         if (not self.state.document.settings.raw_enabled
                 or not self.state.document.settings.file_insertion_enabled):
-            raise self.warning('"%s" directive disabled.' % self.name)
+            raise self.warning(f'"{self.name}" directive disabled.')
 
         # Retrieve the backreferences directory
         config = self.state.document.settings.env.config
@@ -81,9 +81,9 @@ def has_backrefs(obj):
                                 f'{obj}.examples')
 
             # Always remove the heading from the file
-            lines.append("""\
-.. include:: {}
-    :start-after: start-sphx-glr-thumbnails""".format(path))
+            lines.append(f"""\
+.. include:: {path}
+    :start-after: start-sphx-glr-thumbnails""")
 
         # Parse the assembly of `include` and `raw` directives
         text = '\n'.join(lines)
diff --git a/sphinx_gallery/docs_resolv.py b/sphinx_gallery/docs_resolv.py
index b6c92fa1a..07e129188 100644
--- a/sphinx_gallery/docs_resolv.py
+++ b/sphinx_gallery/docs_resolv.py
@@ -346,7 +346,7 @@ def _embed_code_links(app, gallery_conf, gallery_dir):
             for dirpath, _, filenames in os.walk(html_gallery_dir)
             for filename in filenames]
     iterator = status_iterator(
-        flat, 'embedding documentation hyperlinks for %s... ' % gallery_dir,
+        flat, f'embedding documentation hyperlinks for {gallery_dir}... ',
         color='fuchsia', length=len(flat),
         stringify_func=lambda x: os.path.basename(x[1]))
     intersphinx_inv = getattr(app.env, 'intersphinx_named_inventory', dict())
diff --git a/sphinx_gallery/gen_gallery.py b/sphinx_gallery/gen_gallery.py
index 4fe1ea825..119b76e30 100644
--- a/sphinx_gallery/gen_gallery.py
+++ b/sphinx_gallery/gen_gallery.py
@@ -176,14 +176,15 @@ def _fill_gallery_conf_defaults(sphinx_gallery_conf, app=None,
         for rep in capture_repr:
             if rep not in supported_reprs:
                 raise ConfigError("All entries in 'capture_repr' must be one "
-                                  "of %s, got: %s" % (supported_reprs, rep))
+                                  f"of {supported_reprs}, got: {rep}")
     else:
-        raise ConfigError("'capture_repr' must be a tuple, got: %s"
-                          % (type(capture_repr),))
+        raise ConfigError(
+            f"'capture_repr' must be a tuple, got: {type(capture_repr)}"
+        )
     # Check ignore_repr_types
     if not isinstance(gallery_conf['ignore_repr_types'], str):
-        raise ConfigError("'ignore_repr_types' must be a string, got: %s"
-                          % (type(gallery_conf['ignore_repr_types']),))
+        raise ConfigError("'ignore_repr_types' must be a string, got: " +
+                          type(gallery_conf['ignore_repr_types']))
 
     # deal with show_memory
     gallery_conf['memory_base'] = 0.
@@ -230,8 +231,9 @@ def call_memory(func):
                     scraper = getattr(scraper, '_get_sg_image_scraper')
                     scraper = scraper()
                 except Exception as exp:
-                    raise ConfigError('Unknown image scraper %r, got:\n%s'
-                                      % (orig_scraper, exp))
+                    raise ConfigError(
+                        f'Unknown image scraper {orig_scraper!r}, got:\n{exp}'
+                    )
             scrapers[si] = scraper
         if not callable(scraper):
             raise ConfigError(f'Scraper {scraper!r} was not callable')
@@ -257,7 +259,7 @@ def call_memory(func):
         compress_images = [compress_images]
     elif not isinstance(compress_images, (tuple, list)):
         raise ConfigError('compress_images must be a tuple, list, or str, '
-                          'got %s' % (type(compress_images),))
+                          f'got {type(compress_images)}')
     compress_images = list(compress_images)
     allowed_values = ('images', 'thumbnails')
     pops = list()
@@ -267,13 +269,13 @@ def call_memory(func):
                 pops.append(ki)
                 continue
             raise ConfigError('All entries in compress_images must be one of '
-                              '%s or a command-line switch starting with "-", '
-                              'got %r' % (allowed_values, kind))
+                              f'{allowed_values} or a command-line switch '
+                              f'starting with "-", got {kind!r}')
     compress_images_args = [compress_images.pop(p) for p in pops[::-1]]
     if len(compress_images) and not _has_optipng():
         logger.warning(
-            'optipng binaries not found, PNG %s will not be optimized'
-            % (' and '.join(compress_images),))
+            'optipng binaries not found, PNG %s will not be optimized',
+            ' and '.join(compress_images))
         compress_images = ()
     gallery_conf['compress_images'] = compress_images
     gallery_conf['compress_images_args'] = compress_images_args
@@ -286,21 +288,21 @@ def call_memory(func):
     for ri, resetter in enumerate(resetters):
         if isinstance(resetter, str):
             if resetter not in _reset_dict:
-                raise ConfigError('Unknown module resetter named %r'
-                                  % (resetter,))
+                raise ConfigError(
+                    f'Unknown module resetter named {resetter!r}'
+                )
             resetters[ri] = _reset_dict[resetter]
         elif not callable(resetter):
-            raise ConfigError('Module resetter %r was not callable'
-                              % (resetter,))
+            raise ConfigError(f'Module resetter {resetter!r} was not callable')
     gallery_conf['reset_modules'] = tuple(resetters)
 
     if not isinstance(gallery_conf['reset_modules_order'], str):
         raise ConfigError('reset_modules_order must be a str, '
-                          'got %r' % gallery_conf['reset_modules_order'])
+                          f'got {gallery_conf["reset_modules_order"]!r}')
     if gallery_conf['reset_modules_order'] not in ['before', 'after', 'both']:
         raise ConfigError("reset_modules_order must be in"
                           "['before', 'after', 'both'], "
-                          'got %r' % gallery_conf['reset_modules_order'])
+                          f"got {gallery_conf['reset_modules_order']!r}")
 
     del resetters
 
@@ -308,17 +310,17 @@ def call_memory(func):
     first_cell = gallery_conf.get("first_notebook_cell")
     if (not isinstance(first_cell, str)) and (first_cell is not None):
         raise ConfigError("The 'first_notebook_cell' parameter must be type "
-                          "str or None, found type %s" % type(first_cell))
+                          f"str or None, found type {type(first_cell)}")
     # Ensure the last cell text is a string if we have it
     last_cell = gallery_conf.get("last_notebook_cell")
     if (not isinstance(last_cell, str)) and (last_cell is not None):
         raise ConfigError("The 'last_notebook_cell' parameter must be type str"
-                          " or None, found type %s" % type(last_cell))
+                          f" or None, found type {type(last_cell)}")
     # Check pypandoc
     pypandoc = gallery_conf['pypandoc']
     if not isinstance(pypandoc, (dict, bool)):
         raise ConfigError("'pypandoc' parameter must be of type bool or dict,"
-                          "got: %s." % type(pypandoc))
+                          f"got: {type(pypandoc)}.")
     gallery_conf['pypandoc'] = dict() if pypandoc is True else pypandoc
     has_pypandoc, version = _has_pypandoc()
     if isinstance(gallery_conf['pypandoc'], dict) and has_pypandoc is None:
@@ -327,7 +329,7 @@ def call_memory(func):
         gallery_conf['pypandoc'] = False
     elif isinstance(gallery_conf['pypandoc'], dict):
         logger.info("Using pandoc version: %s to convert rst text blocks to "
-                    "markdown for .ipynb files" % (version,))
+                    "markdown for .ipynb files", version)
     else:
         logger.info("Using Sphinx-Gallery to convert rst text blocks to "
                     "markdown for .ipynb files.")
@@ -336,8 +338,7 @@ def call_memory(func):
         for key in pypandoc:
             if key not in accepted_keys:
                 raise ConfigError("'pypandoc' only accepts the following key "
-                                  "values: %s, got: %s."
-                                  % (accepted_keys, key))
+                                  f"values: {accepted_keys}, got: {key}.")
 
     gallery_conf['titles'] = {}
     # Ensure 'backreferences_dir' is str, pathlib.Path or None
@@ -346,7 +347,7 @@ def call_memory(func):
             (backref is not None):
         raise ConfigError("The 'backreferences_dir' parameter must be of type "
                           "str, pathlib.Path or None, "
-                          "found type %s" % type(backref))
+                          f"found type {type(backref)}")
     # if 'backreferences_dir' is pathlib.Path, make str for Python <=3.5
     # compatibility
     if isinstance(backref, pathlib.Path):
@@ -360,25 +361,26 @@ def call_memory(func):
         gallery_conf.get('jupyterlite', {}), app)
 
     if not isinstance(gallery_conf['css'], (list, tuple)):
-        raise ConfigError('gallery_conf["css"] must be list or tuple, got %r'
-                          % (gallery_conf['css'],))
+        raise ConfigError('gallery_conf["css"] must be list or tuple, got '
+                          f'{gallery_conf["css"]!r}')
     for css in gallery_conf['css']:
         if css not in _KNOWN_CSS:
-            raise ConfigError('Unknown css %r, must be one of %r'
-                              % (css, _KNOWN_CSS))
+            raise ConfigError(
+                f'Unknown css {css!r}, must be one of {_KNOWN_CSS!r}'
+            )
         if gallery_conf['app'] is not None:  # can be None in testing
             gallery_conf['app'].add_css_file(css + '.css')
 
     # check API usage
     if not isinstance(gallery_conf['api_usage_ignore'], str):
         raise ConfigError('gallery_conf["api_usage_ignore"] must be str, '
-                          'got %s' % type(gallery_conf['api_usage_ignore']))
+                          f'got {type(gallery_conf["api_usage_ignore"])}')
 
     if not isinstance(gallery_conf['show_api_usage'], bool) and \
             gallery_conf['show_api_usage'] != 'unused':
         raise ConfigError(
             'gallery_conf["show_api_usage"] must be True, False or "unused", '
-            'got %s' % gallery_conf['show_api_usage'])
+            f'got {gallery_conf["show_api_usage"]}')
 
     _update_gallery_conf_exclude_implicit_doc(gallery_conf)
 
@@ -456,7 +458,7 @@ def _format_toctree(items, includehidden=False):
 """
     st += """
 
-   %s\n""" % "\n   ".join(items)
+   {}\n""".format("\n   ".join(items))
 
     st += "\n"
 
@@ -695,7 +697,7 @@ def write_computation_times(gallery_conf, target_dir, costs):
         return
     target_dir_clean = os.path.relpath(
         target_dir, gallery_conf['src_dir']).replace(os.path.sep, '_')
-    new_ref = 'sphx_glr_%s_sg_execution_times' % target_dir_clean
+    new_ref = f'sphx_glr_{target_dir_clean}_sg_execution_times'
     with codecs.open(os.path.join(target_dir, 'sg_execution_times.rst'), 'w',
                      encoding='utf-8') as fid:
         fid.write(SPHX_GLR_COMP_TIMES.format(new_ref))
@@ -924,7 +926,7 @@ def get_entry_type(entry):
                     '    :layout: neato\n\n')
 
             for module in used_modules:
-                logger.info(f'Making API usage graph for {module}')
+                logger.info('Making API usage graph for %s', module)
                 # select and format entries for this module
                 entries = dict()
                 for entry, ref in used_api_entries.items():
@@ -1015,7 +1017,7 @@ def touch_empty_backreferences(app, what, name, obj, options, lines):
     examples_path = os.path.join(app.srcdir,
                                  app.config.sphinx_gallery_conf[
                                      "backreferences_dir"],
-                                 "%s.examples" % name)
+                                 f"{name}.examples")
 
     if not os.path.exists(examples_path):
         # touch file
@@ -1095,12 +1097,11 @@ def summarize_failing_examples(app, exception):
                 '    gallery_conf["filename_pattern"] = %r\n'
                 '    gallery_conf["ignore_pattern"]   = %r\n'
                 '\nafter excluding %d file%s that had previously been run '
-                '(based on MD5).\n'
-                % (n_good, n_tot, 's' if n_tot != 1 else '',
-                   gallery_conf['filename_pattern'],
-                   gallery_conf['ignore_pattern'],
-                   n_stale, 's' if n_stale != 1 else '',
-                   ),
+                '(based on MD5).\n',
+                n_good, n_tot, 's' if n_tot != 1 else '',
+                gallery_conf['filename_pattern'],
+                gallery_conf['ignore_pattern'],
+                n_stale, 's' if n_stale != 1 else '',
                 color='brown')
 
     if fail_msgs:
@@ -1143,7 +1144,7 @@ def check_duplicate_filenames(files):
         logger.warning(
             'Duplicate example file name(s) found. Having duplicate file '
             'names will break some links. '
-            'List of files: {}'.format(sorted(dup_names),))
+            'List of files: %s', sorted(dup_names))
 
 
 def check_spaces_in_filenames(files):
@@ -1154,7 +1155,7 @@ def check_spaces_in_filenames(files):
         logger.warning(
             'Example file name(s) with space(s) found. Having space(s) in '
             'file names will break some links. '
-            'List of files: {}'.format(sorted(files_with_space),))
+            'List of files: %s', sorted(files_with_space))
 
 
 def get_default_config_value(key):
diff --git a/sphinx_gallery/gen_rst.py b/sphinx_gallery/gen_rst.py
index fbf6e9eb7..43f94c29a 100644
--- a/sphinx_gallery/gen_rst.py
+++ b/sphinx_gallery/gen_rst.py
@@ -246,8 +246,7 @@ def extract_intro_and_title(filename, docstring):
 
     if match is None:
         raise ExtensionError(
-            'Could not find a title in first paragraph:\n{}'.format(
-                title_paragraph))
+            f'Could not find a title in first paragraph:\n{title_paragraph}')
     title = match.group(0).strip()
     # Use the title if no other paragraphs are provided
     intro_paragraph = title if len(paragraphs) < 2 else paragraphs[1]
@@ -313,7 +312,7 @@ def save_thumbnail(image_path_template, src_file, script_vars, file_conf,
         if not isinstance(thumbnail_number, int):
             raise ExtensionError(
                 'sphinx_gallery_thumbnail_number setting is not a number, '
-                'got %r' % (thumbnail_number,))
+                f'got {thumbnail_number!r}')
         # negative index means counting from the last one
         if thumbnail_number < 0:
             thumbnail_number += len(script_vars["image_path_iterator"]) + 1
@@ -453,7 +452,7 @@ def generate_dir_rst(
     build_target_dir = os.path.relpath(target_dir, gallery_conf['src_dir'])
     iterator = status_iterator(
         sorted_listdir,
-        'generating gallery for %s... ' % build_target_dir,
+        f'generating gallery for {build_target_dir}... ',
         length=len(sorted_listdir))
     for fname in iterator:
         intro, title, cost = generate_file_rst(
@@ -484,7 +483,7 @@ def generate_dir_rst(
         with codecs.open(subsection_index_path, 'w', encoding='utf-8') as (
             findex
         ):
-            findex.write("""\n\n.. _sphx_glr_{}:\n\n""".format(
+            findex.write("\n\n.. _sphx_glr_{}:\n\n".format(
                 head_ref.replace(os.path.sep, '_')
             ))
             findex.write(subsection_index_content)
@@ -501,8 +500,8 @@ def generate_dir_rst(
 .. toctree::
    :hidden:
 
-   %s\n
-""" % "\n   ".join(subsection_toctree_filenames)
+   {}\n
+""".format("\n   ".join(subsection_toctree_filenames))
                 findex.write(subsection_index_toctree)
 
     if have_index_rst:
@@ -662,7 +661,7 @@ def _get_memory_base(gallery_conf):
         sleep, timeout = (0.5, 1)
     proc = subprocess.Popen(
         [sys.executable, '-c',
-            'import time, sys; time.sleep(%s); sys.exit(0)' % sleep],
+            f'import time, sys; time.sleep({sleep}); sys.exit(0)'],
         close_fds=True)
     memories = memory_usage(proc, interval=1e-3, timeout=timeout)
     kwargs = dict(timeout=timeout) if sys.version_info >= (3, 5) else {}
@@ -784,9 +783,7 @@ def _get_code_output(is_last_expr, example_globals, gallery_conf, logging_tee,
     else:
         captured_html = ''
 
-    code_output = "\n{}\n\n{}\n{}\n\n".format(
-        images_rst, captured_std, captured_html
-    )
+    code_output = f"\n{images_rst}\n\n{captured_std}\n{captured_html}\n\n"
     return code_output
 
 
@@ -1086,7 +1083,7 @@ def generate_file_rst(fname, target_dir, src_dir, gallery_conf,
             if type(dummy_image) is not int:
                 raise ExtensionError(
                     'sphinx_gallery_dummy_images setting is not a number, '
-                    'got %r' % (dummy_image,))
+                    'got {dummy_image!r}')
 
             image_path_iterator = script_vars['image_path_iterator']
             stock_img = os.path.join(glr_path_static(), 'no_image.png')
@@ -1302,8 +1299,7 @@ def save_rst_example(example_rst, example_file, time_elapsed,
     fname = os.path.basename(example_file)
 
     if gallery_conf['show_memory']:
-        example_rst += ("**Estimated memory usage:** {: .0f} MB\n\n"
-                        .format(memory_used))
+        example_rst += f"**Estimated memory usage:** {memory_used: .0f} MB\n\n"
 
     # Generate a binder URL if specified
     binder_badge_rst = ''
diff --git a/sphinx_gallery/interactive_example.py b/sphinx_gallery/interactive_example.py
index 48b5d9d9b..99ec55e7a 100644
--- a/sphinx_gallery/interactive_example.py
+++ b/sphinx_gallery/interactive_example.py
@@ -233,8 +233,9 @@ def check_binder_conf(binder_conf):
             missing_values.append(val)
 
     if len(missing_values) > 0:
-        raise ConfigError('binder_conf is missing values for: {}'.format(
-            missing_values))
+        raise ConfigError(
+            f'binder_conf is missing values for: {missing_values}'
+        )
 
     for key in binder_conf.keys():
         if key not in (req_values + optional_values):
diff --git a/sphinx_gallery/notebook.py b/sphinx_gallery/notebook.py
index bbe49ba7d..5ba71ca40 100644
--- a/sphinx_gallery/notebook.py
+++ b/sphinx_gallery/notebook.py
@@ -209,10 +209,9 @@ def generate_image_src(image_path, gallery_conf, target_dir):
                 data = base64.b64encode(image_file.read())
         except OSError:
             raise ExtensionError(
-                'Unable to open {} to generate notebook data URI'
-                ''.format(full_path))
+                f'Unable to open {full_path} to generate notebook data URI')
         mime_type = mimetypes.guess_type(full_path)
-        return 'data:{};base64,{}'.format(mime_type[0], data.decode('ascii'))
+        return f"data:{mime_type[0]};base64,{data.decode('ascii')}"
 
 
 def jupyter_notebook(script_blocks, gallery_conf, target_dir):
diff --git a/sphinx_gallery/scrapers.py b/sphinx_gallery/scrapers.py
index 0de09aa1f..8fa19d2d9 100644
--- a/sphinx_gallery/scrapers.py
+++ b/sphinx_gallery/scrapers.py
@@ -339,17 +339,16 @@ def save_figures(block, block_vars, gallery_conf):
     for scraper in gallery_conf['image_scrapers']:
         rst = scraper(block, block_vars, gallery_conf)
         if not isinstance(rst, str):
-            raise ExtensionError('rst from scraper %r was not a string, '
-                                 'got type %s:\n%r'
-                                 % (scraper, type(rst), rst))
+            raise ExtensionError(f'rst from scraper {scraper!r} was not a '
+                                 f'string, got type {type(rst)}:\n{rst!r}')
         n_new = len(image_path_iterator) - prev_count
         for ii in range(n_new):
             current_path, _ = _find_image_ext(
                 image_path_iterator.paths[prev_count + ii])
             if not os.path.isfile(current_path):
                 raise ExtensionError(
-                    'Scraper %s did not produce expected image:'
-                    '\n%s' % (scraper, current_path))
+                    f'Scraper {scraper} did not produce expected image:'
+                    f'\n{current_path}')
         all_rst += rst
     return all_rst
 
diff --git a/sphinx_gallery/tests/conftest.py b/sphinx_gallery/tests/conftest.py
index 0e90e0b21..e2cb3ca3c 100644
--- a/sphinx_gallery/tests/conftest.py
+++ b/sphinx_gallery/tests/conftest.py
@@ -178,16 +178,16 @@ def sphinx_app_wrapper(tmpdir, conf_file, req_mpl, req_pil):
     shutil.copytree(os.path.join(_fixturedir, "src"),
                     os.path.join(str(tmpdir), "examples"))
 
-    base_config = """
+    base_config = f"""
 import os
 import sphinx_gallery
-extensions = {!r}
+extensions = {conf_file['extensions']!r}
 exclude_patterns = ['_build']
 source_suffix = '.rst'
 master_doc = 'index'
 # General information about the project.
-project = u'Sphinx-Gallery <Tests>'\n\n
-""".format(conf_file['extensions'])
+project = 'Sphinx-Gallery <Tests>'\n\n
+"""
     with open(os.path.join(srcdir, "conf.py"), "w") as conffile:
         conffile.write(base_config + conf_file['content'])
 
diff --git a/sphinx_gallery/tests/test_full.py b/sphinx_gallery/tests/test_full.py
index 4cc65cf8e..12f54fc22 100644
--- a/sphinx_gallery/tests/test_full.py
+++ b/sphinx_gallery/tests/test_full.py
@@ -96,7 +96,7 @@ def test_timings(sphinx_app):
     with codecs.open(timings_rst, 'r', 'utf-8') as fid:
         content = fid.read()
     assert ':ref:`sphx_glr_auto_examples_plot_numpy_matplotlib.py`' in content
-    parenthetical = '(``{}``)'.format('plot_numpy_matplotlib.py')
+    parenthetical = "(``plot_numpy_matplotlib.py``)"
     assert parenthetical in content
     # HTML output
     timings_html = op.join(out_dir, 'auto_examples',
@@ -108,7 +108,7 @@ def test_timings(sphinx_app):
     # printed
     status = sphinx_app._status.getvalue()
     fname = op.join('..', 'examples', 'plot_numpy_matplotlib.py')
-    assert ('- %s: ' % fname) in status
+    assert f'- {fname}: ' in status
 
 
 def test_api_usage(sphinx_app):
@@ -142,7 +142,7 @@ def test_api_usage(sphinx_app):
     # printed
     status = sphinx_app._status.getvalue()
     fname = op.join('..', 'examples', 'plot_numpy_matplotlib.py')
-    assert ('- %s: ' % fname) in status
+    assert f'- {fname}: ' in status
 
 
 def test_optipng(sphinx_app):
@@ -165,7 +165,7 @@ def test_junit(sphinx_app, tmpdir):
         contents = fid.read()
     assert contents.startswith('<?xml')
     assert 'errors="0" failures="0"' in contents
-    assert 'tests="%d"' % (N_EXAMPLES,) in contents
+    assert f'tests="{N_EXAMPLES}"' in contents
     assert 'local_module' not in contents  # it's not actually run as an ex
     assert 'expected example failure' in contents
     assert '<failure message' not in contents
@@ -221,7 +221,7 @@ def test_run_sphinx(sphinx_app):
     for f in files_to_check:
         assert op.isfile(out_dir + '/' + f)
     status = sphinx_app._status.getvalue()
-    assert 'executed %d out of %d' % (N_GOOD, N_EXAMPLES) in status
+    assert f'executed {N_GOOD} out of {N_EXAMPLES}' in status
     assert 'after excluding 0' in status
     # intentionally have a bad URL in references
     warning = sphinx_app._warning.getvalue()
@@ -303,17 +303,16 @@ def test_image_formats(sphinx_app):
             ('plot_numpy_matplotlib', 'png', [1], None),
             ('plot_animation', 'png', [1, 3], 'function Animation'),
             ('plot_webp', 'webp', [1], None)):
-        html_fname = op.join(generated_examples_dir, '%s.html' % ex)
+        html_fname = op.join(generated_examples_dir, f'{ex}.html')
         with codecs.open(html_fname, 'r', 'utf-8') as fid:
             html = fid.read()
         for num in nums:
-            img_fname0 = '../_images/sphx_glr_%s_%03d.%s' % (ex, num, ext)
+            img_fname0 = f'../_images/sphx_glr_{ex}_{num:03}.{ext}'
             file_fname = op.join(generated_examples_dir, img_fname0)
             assert op.isfile(file_fname), file_fname
             want_html = f'src="{img_fname0}"'
             assert want_html in html
-            img_fname2 = ('../_images/sphx_glr_%s_%03d_2_00x.%s' %
-                          (ex, num, ext))
+            img_fname2 = f'../_images/sphx_glr_{ex}_{num:03}_2_00x.{ext}'
             file_fname2 = op.join(generated_examples_dir, img_fname2)
             want_html = f'srcset="{img_fname0}, {img_fname2} 2.00x"'
             if ext in ('png', 'jpg', 'svg', 'webp'):
@@ -414,7 +413,7 @@ def test_embed_links_and_styles(sphinx_app):
     assert 'class="sphx-glr-signature"' in lines
     assert 'class="sphx-glr-timing"' in lines
     for kind in ('python', 'jupyter'):
-        assert 'class="sphx-glr-download sphx-glr-download-%s docutils container"' % kind in lines  # noqa:E501
+        assert f'class="sphx-glr-download sphx-glr-download-{kind} docutils container"' in lines  # noqa:E501
 
     # highlight language
     fname = op.join(src_dir, 'auto_examples', 'plot_numpy_matplotlib.rst')
@@ -725,7 +724,7 @@ def _rerun(how, src_dir, conf_dir, out_dir, toctrees_dir,
     flags = re.MULTILINE | re.DOTALL
     # for some reason, setting "confoverrides" above causes Sphinx to show
     # all targets out of date, even though they haven't been modified...
-    want = '.*targets for %s source files that are out of date$.*' % N_RST
+    want = f'.*targets for {N_RST} source files that are out of date$.*'
     assert re.match(want, status, flags) is not None, lines
     # ... but then later detects that only some have actually changed:
     # Linux: 8 changed when how='run_stale', 9 when how='modify'.
diff --git a/sphinx_gallery/tests/test_gen_gallery.py b/sphinx_gallery/tests/test_gen_gallery.py
index 0e9df6ad5..196288a2b 100644
--- a/sphinx_gallery/tests/test_gen_gallery.py
+++ b/sphinx_gallery/tests/test_gen_gallery.py
@@ -188,7 +188,7 @@ def _check_order(sphinx_app, key):
 
     index_fname = os.path.join(sphinx_app.outdir, '..', 'ex', 'index.rst')
     order = list()
-    regex = '.*:%s=(.):.*' % key
+    regex = f'.*:{key}=(.):.*'
     with codecs.open(index_fname, 'r', 'utf-8') as fid:
         for line in fid:
             if 'sphx-glr-thumbcontainer' in line:
diff --git a/sphinx_gallery/tests/test_gen_rst.py b/sphinx_gallery/tests/test_gen_rst.py
index a63a720b9..03b3bc583 100644
--- a/sphinx_gallery/tests/test_gen_rst.py
+++ b/sphinx_gallery/tests/test_gen_rst.py
@@ -49,13 +49,13 @@
     'import sys',
     'from warnings import warn',
     'x, y = 1, 2',
-    'print(u"Óscar output") # need some code output',
+    'print("Óscar output") # need some code output',
     'logger = logging.getLogger()',
     'logger.setLevel(logging.INFO)',
     'lh = logging.StreamHandler(sys.stdout)',
     'lh.setFormatter(logging.Formatter("log:%(message)s"))',
     'logger.addHandler(lh)',
-    'logger.info(u"Óscar")',
+    'logger.info("Óscar")',
     'print(r"$\\langle n_\\uparrow n_\\downarrow \\rangle$")',
     'warn("WarningsAbound", RuntimeWarning)',
 ]
diff --git a/sphinx_gallery/utils.py b/sphinx_gallery/utils.py
index a5c883a9b..edc6b7e5d 100644
--- a/sphinx_gallery/utils.py
+++ b/sphinx_gallery/utils.py
@@ -34,7 +34,7 @@ def _get_image():
         except ImportError:
             raise ExtensionError(
                 'Could not import pillow, which is required '
-                'to rescale images (e.g., for thumbnails): %s' % (exc,))
+                f'to rescale images (e.g., for thumbnails): {exc}')
     return Image
 
 
@@ -126,8 +126,8 @@ def replace_py_ipynb(fname):
     allowed_extension = '.py'
     if extension != allowed_extension:
         raise ValueError(
-            "Unrecognized file extension, expected %s, got %s"
-            % (allowed_extension, extension))
+            f"Unrecognized file extension, expected {allowed_extension}, "
+            f"got {extension}")
     new_extension = '.ipynb'
     return f'{fname_prefix}{new_extension}'