diff --git a/doc/intro.rst b/doc/intro.rst
index 6786288..fe8effc 100644
--- a/doc/intro.rst
+++ b/doc/intro.rst
@@ -333,11 +333,11 @@ Handlers are given a `progress` object containing a number of useful fields.
 For example::
 
    def eval_handler(image, progress):
-       print('run time so far (secs) = {}'.format(progress.run))
-       print('estimated time of arrival (secs) = {}'.format(progress.eta))
-       print('total number of pels to process = {}'.format(progress.tpels))
-       print('number of pels processed so far = {}'.format(progress.npels))
-       print('percent complete = {}'.format(progress.percent))
+       print(f'   run = {progress.run} (seconds of run time)')
+       print(f'   eta = {progress.eta} (estimated seconds left)')
+       print(f'   tpels = {progress.tpels} (total number of pels)')
+       print(f'   npels = {progress.npels} (number of pels computed so far)')
+       print(f'   percent = {progress.percent} (percent complete)')
 
 Use :meth:`.Image.set_kill` on the image to stop computation early. 
 
diff --git a/examples/pil-numpy-pyvips.py b/examples/pil-numpy-pyvips.py
index 1bd1b39..b040697 100755
--- a/examples/pil-numpy-pyvips.py
+++ b/examples/pil-numpy-pyvips.py
@@ -8,7 +8,7 @@
 import numpy as np
 
 if len(sys.argv) != 3:
-    print('usage: {0} input-filename output-filename'.format(sys.argv[0]))
+    print(f'usage: {sys.argv[0]} input-filename output-filename')
     sys.exit(-1)
 
 
diff --git a/examples/progress.py b/examples/progress.py
index 414d709..8307bb1 100755
--- a/examples/progress.py
+++ b/examples/progress.py
@@ -4,7 +4,7 @@
 
 
 def progress_print(name, progress):
-    print(f'signal {name}:'.format(name))
+    print(f'signal {name}:')
     print(f'   run = {progress.run} (seconds of run time)')
     print(f'   eta = {progress.eta} (estimated seconds left)')
     print(f'   tpels = {progress.tpels} (total number of pels)')
diff --git a/examples/soak-test.py b/examples/soak-test.py
index 79ff23d..8a7ccf9 100755
--- a/examples/soak-test.py
+++ b/examples/soak-test.py
@@ -7,7 +7,7 @@
 pyvips.cache_set_max(0)
 
 for i in range(1000):
-    print("loop {0} ...".format(i))
+    print(f"loop {i} ...")
     im = pyvips.Image.new_from_file(sys.argv[1])
     im = im.embed(100, 100, 3000, 3000, extend="mirror")
     im.write_to_file("x.v")
diff --git a/examples/try5.py b/examples/try5.py
index 9aade16..ebc307f 100755
--- a/examples/try5.py
+++ b/examples/try5.py
@@ -11,7 +11,7 @@
 
 def should_equal(test, a, b):
     if abs(a - b) > 0.01:
-        print('%s: seen %g and %g' % (test, a, b))
+        print(f'{test}: seen {a:g} and {b:g}')
         sys.exit(1)
 
 
diff --git a/pyvips/__init__.py b/pyvips/__init__.py
index 323992b..82fe1cf 100644
--- a/pyvips/__init__.py
+++ b/pyvips/__init__.py
@@ -32,9 +32,8 @@
     lib_minor = vips_lib.vips_version(1)
     wrap_major = vips_lib.VIPS_MAJOR_VERSION
     wrap_minor = vips_lib.VIPS_MINOR_VERSION
-    logger.debug('Module generated for libvips %s.%s' %
-                 (wrap_major, wrap_minor))
-    logger.debug('Linked to libvips %s.%s' % (lib_major, lib_minor))
+    logger.debug(f'Module generated for libvips {wrap_major}.{wrap_minor}')
+    logger.debug(f'Linked to libvips {lib_major}.{lib_minor}')
 
     if wrap_major != lib_major or wrap_minor != lib_minor:
         raise Exception('bad wrapper version')
@@ -42,7 +41,7 @@
     API_mode = True
 
 except Exception as e:
-    logger.debug('Binary module load failed: %s' % e)
+    logger.debug(f'Binary module load failed: {e}')
     logger.debug('Falling back to ABI mode')
 
     from cffi import FFI
@@ -141,14 +140,14 @@ class GLogLevelFlags(object):
     @ffi.def_extern()
     def _log_handler_callback(domain, level, message, user_data):
         logger.log(GLogLevelFlags.LEVEL_TO_LOGGER[level],
-                   '{0}: {1}'.format(_to_string(domain), _to_string(message)))
+                   f'{_to_string(domain)}: {_to_string(message)}')
 
     # keep a ref to the cb to stop it being GCd
     _log_handler_cb = glib_lib._log_handler_callback
 else:
     def _log_handler_callback(domain, level, message, user_data):
         logger.log(GLogLevelFlags.LEVEL_TO_LOGGER[level],
-                   '{0}: {1}'.format(_to_string(domain), _to_string(message)))
+                   f'{_to_string(domain)}: {_to_string(message)}')
 
     # keep a ref to the cb to stop it being GCd
     _log_handler_cb = ffi.callback('GLogFunc', _log_handler_callback)
diff --git a/pyvips/error.py b/pyvips/error.py
index 962a1f6..8e78b78 100644
--- a/pyvips/error.py
+++ b/pyvips/error.py
@@ -68,7 +68,7 @@ def __init__(self, message, detail=None):
         logger.debug('Error %s %s', self.message, self.detail)
 
     def __str__(self):
-        return '{0}\n  {1}'.format(self.message, self.detail)
+        return f'{self.message}\n  {self.detail}'
 
 
 __all__ = [
diff --git a/pyvips/gobject.py b/pyvips/gobject.py
index 706424c..93c6564 100644
--- a/pyvips/gobject.py
+++ b/pyvips/gobject.py
@@ -159,7 +159,7 @@ def new_pointer_from_gtype(gtype):
 
         pointer = gobject_lib.g_object_new(gtype, ffi.NULL)
         if pointer == ffi.NULL:
-            raise Error("can't create {0}".format(type_name(gtype)))
+            raise Error(f"can't create {type_name(gtype)}")
 
         return pointer
 
@@ -176,7 +176,7 @@ def signal_connect(self, name, callback):
         """
 
         if name not in _marshalers:
-            raise Error('unsupported signal "{0}"'.format(name))
+            raise Error(f'unsupported signal "{name}"')
 
         go = ffi.cast('GObject *', self.pointer)
         handle = ffi.new_handle(callback)
diff --git a/pyvips/gvalue.py b/pyvips/gvalue.py
index 88f2360..04069e8 100644
--- a/pyvips/gvalue.py
+++ b/pyvips/gvalue.py
@@ -84,7 +84,7 @@ def gtype_to_python(gtype):
             name = type_name(gtype)
             if name.startswith('Vips'):
                 name = name[4:]
-            return "Union[str, %s]" % name
+            return f"Union[str, {name}]"
         if gtype in GValue._gtype_to_python:
             return GValue._gtype_to_python[gtype]
         if fundamental in GValue._gtype_to_python:
diff --git a/pyvips/pyvips_build.py b/pyvips/pyvips_build.py
index 788b479..e76c13b 100644
--- a/pyvips/pyvips_build.py
+++ b/pyvips/pyvips_build.py
@@ -32,9 +32,10 @@
 ''' if major == 8 and minor < 6 else ''
 
 ffibuilder.set_source("_libvips",
-    r"""
+    f"""
         #include <vips/vips.h>
-    """ + compat,
+        {compat}
+    """,
     **pkgconfig.parse('vips'))
 
 features = {
diff --git a/pyvips/vdecls.py b/pyvips/vdecls.py
index 547debb..4cbdad9 100644
--- a/pyvips/vdecls.py
+++ b/pyvips/vdecls.py
@@ -472,7 +472,7 @@ def cdefs(features):
 
     # add contents of features as a comment ... handy for debugging
     for key, value in features.items():
-        code += '//%s = %s\n' % (key, value)
+        code += f'//{key} = {value}\n'
 
     return code
 
diff --git a/pyvips/vimage.py b/pyvips/vimage.py
index 46f1ee1..a4ab8cd 100644
--- a/pyvips/vimage.py
+++ b/pyvips/vimage.py
@@ -181,7 +181,7 @@ def _guess_interpretation(bands, format):
     """
 
     if format not in FORMAT_TO_TYPESTR:
-        raise ValueError('Unknown format: {}'.format(format))
+        raise ValueError(f'Unknown format: {format}')
     if not isinstance(bands, int) or bands < 1:
         raise ValueError('Number of bands must be a positive integer.')
 
@@ -323,7 +323,7 @@ def new_from_file(vips_filename, **kwargs):
 
         pointer = vips_lib.vips_foreign_find_load(vips_filename)
         if pointer == ffi.NULL:
-            raise Error('unable to load from file {0}'.format(vips_filename))
+            raise Error(f'unable to load from file {vips_filename}')
         name = _to_string(pointer)
 
         return pyvips.Operation.call(name, filename,
@@ -493,8 +493,7 @@ def new_from_array(cls, obj, scale=1.0, offset=0.0, interpretation=None):
             if ndim > 3:
                 raise ValueError('array has more than 3 dimensions')
             if typestr not in TYPESTR_TO_FORMAT:
-                raise ValueError('conversion from {0} not supported'
-                                 .format(typestr))
+                raise ValueError(f'conversion from {typestr} not supported')
 
             if ndim == 0:
                 width = 1
@@ -776,7 +775,7 @@ def write_to_file(self, vips_filename, **kwargs):
 
         pointer = vips_lib.vips_foreign_find_save(vips_filename)
         if pointer == ffi.NULL:
-            raise Error('unable to write to file {0}'.format(vips_filename))
+            raise Error(f'unable to write to file {vips_filename}')
         name = _to_string(pointer)
 
         return pyvips.Operation.call(name, self, filename,
@@ -1038,7 +1037,7 @@ def get(self, name):
         result = vips_lib.vips_image_get(self.pointer, _to_bytes(name),
                                          gv.pointer)
         if result != 0:
-            raise Error('unable to get {0}'.format(name))
+            raise Error(f'unable to get {name}')
 
         return gv.get()
 
@@ -1107,8 +1106,8 @@ def set(self, name, value):
         """
         gtype = self.get_typeof(name)
         if gtype == 0:
-            raise Error('metadata item {0} does not exist - '
-                        'use set_type() to create and set'.format(name))
+            raise Error(f'metadata item {name} does not exist -'
+                        ' use set_type() to create and set')
         self.set_type(gtype, name, value)
 
     def remove(self, name):
@@ -1143,7 +1142,7 @@ def tolist(self):
 
         row_els = self.width if not is_complex else 2 * self.width
 
-        rowfmt = '{0}{1}'.format(row_els, FORMAT_TO_PYFORMAT[self.format])
+        rowfmt = f'{row_els}{FORMAT_TO_PYFORMAT[self.format]}'
         buf = self.write_to_memory()
 
         lst = [list(row) for row in struct.iter_unpack(rowfmt, buf)]
@@ -1261,9 +1260,8 @@ def __repr__(self):
             array = self.tolist()
             return repr(array)
         else:
-            return ('<pyvips.Image {0}x{1} {2}, {3} bands, {4}>'.
-                    format(self.width, self.height, self.format, self.bands,
-                           self.interpretation))
+            return (f'<pyvips.Image {self.width}x{self.height} {self.format}, '
+                    f'{self.bands} bands, {self.interpretation}>')
 
     def __getattr__(self, name):
         """Divert unknown names to libvips.
diff --git a/pyvips/vinterpolate.py b/pyvips/vinterpolate.py
index 5b0f2c7..f111469 100644
--- a/pyvips/vinterpolate.py
+++ b/pyvips/vinterpolate.py
@@ -35,7 +35,7 @@ def new(name):
 
         vi = vips_lib.vips_interpolate_new(_to_bytes(name))
         if vi == ffi.NULL:
-            raise Error('no such interpolator {0}'.format(name))
+            raise Error(f'no such interpolator {name}')
 
         return Interpolate(vi)
 
diff --git a/pyvips/voperation.py b/pyvips/voperation.py
index db66b15..849fcb8 100644
--- a/pyvips/voperation.py
+++ b/pyvips/voperation.py
@@ -188,7 +188,7 @@ def __init__(self, pointer):
     def new_from_name(operation_name):
         vop = vips_lib.vips_operation_new(_to_bytes(operation_name))
         if vop == ffi.NULL:
-            raise Error('no such operation {0}'.format(operation_name))
+            raise Error(f'no such operation {operation_name}')
         return Operation(vop)
 
     def set(self, name, flags, match_image, value):
@@ -232,10 +232,8 @@ def call(operation_name, *args, **kwargs):
         intro = Introspect.get(operation_name)
 
         if len(intro.required_input) != len(args):
-            raise Error('{0} needs {1} arguments, but {2} given'
-                        .format(operation_name,
-                                len(intro.required_input),
-                                len(args)))
+            raise Error(f'{operation_name} needs {len(intro.required_input)} '
+                        f'arguments, but {len(args)} given')
 
         op = Operation.new_from_name(operation_name)
 
@@ -243,7 +241,7 @@ def call(operation_name, *args, **kwargs):
         # overridden
         string_options = kwargs.pop('string_options', '')
         if not op.set_string(string_options):
-            raise Error('unable to call {0}'.format(operation_name))
+            raise Error(f'unable to call {operation_name}')
 
         # the first image argument is the thing we expand constants to
         # match ... look inside tables for images, since we may be passing
@@ -283,8 +281,8 @@ def add_reference(x):
         for name in kwargs:
             if (name not in intro.optional_input and
                     name not in intro.optional_output):
-                raise Error('{0} does not support optional argument {1}'
-                            .format(operation_name, name))
+                raise Error(f'{operation_name} does not support optional '
+                            f'argument {name}')
 
             value = kwargs[name]
             details = intro.details[name]
@@ -300,7 +298,7 @@ def add_reference(x):
         vop = vips_lib.vips_cache_operation_build(op.pointer)
         if vop == ffi.NULL:
             vips_lib.vips_object_unref_outputs(op.vobject)
-            raise Error('unable to call {0}'.format(operation_name))
+            raise Error(f'unable to call {operation_name}')
         op = Operation(vop)
 
         # attach all input refs to output x
@@ -353,7 +351,7 @@ def generate_docstring(operation_name):
         intro = Introspect.get(operation_name)
         if (intro.flags & _OPERATION_DEPRECATED) != 0:
             raise Error('No such operator.',
-                        'operator "{0}" is deprecated'.format(operation_name))
+                        f'operator "{operation_name}" is deprecated')
 
         result = intro.description[0].upper() + intro.description[1:] + '.\n\n'
         result += 'Example:\n'
@@ -417,7 +415,7 @@ def generate_sphinx(operation_name):
         intro = Introspect.get(operation_name)
         if (intro.flags & _OPERATION_DEPRECATED) != 0:
             raise Error('No such operator.',
-                        'operator "{0}" is deprecated'.format(operation_name))
+                        f'operator "{operation_name}" is deprecated')
 
         if intro.member_x is not None:
             result = '.. method:: '
@@ -451,14 +449,13 @@ def generate_sphinx(operation_name):
 
         for name in intro.method_args + intro.doc_optional_input:
             details = intro.details[name]
-            result += (':param {0}: {1}\n'.
-                       format(name, details['blurb']))
-            result += (':type {0}: {1}\n'.
-                       format(name, GValue.gtype_to_python(details['type'])))
+            result += f':param {name}: {details["blurb"]}\n'
+            result += (f':type {name}: '
+                       f'{GValue.gtype_to_python(details["type"])}\n')
         for name in intro.doc_optional_output:
-            result += (':param {0}: enable output: {1}\n'.
-                       format(name, intro.details[name]['blurb']))
-            result += (':type {0}: bool\n'.format(name))
+            result += (f':param {name}: '
+                       f'enable output: {intro.details[name]["blurb"]}\n')
+            result += f':type {name}: bool\n'
 
         output_types = [GValue.gtype_to_python(intro.details[name]['type'])
                         for name in intro.required_output]
@@ -532,7 +529,7 @@ def add_name(gtype, a, b):
         print('   .. autosummary::')
         print('      :nosignatures:\n')
         for name in all_names:
-            print('      ~{0}'.format(name))
+            print(f'      ~{name}')
         print()
 
         # Output docs
diff --git a/pyvips/vsource.py b/pyvips/vsource.py
index a1b7d50..d4f2386 100644
--- a/pyvips/vsource.py
+++ b/pyvips/vsource.py
@@ -35,8 +35,7 @@ def new_from_descriptor(descriptor):
         # sources are mutable, so we can't use the cache
         pointer = vips_lib.vips_source_new_from_descriptor(descriptor)
         if pointer == ffi.NULL:
-            raise Error("can't create source from descriptor {0}"
-                        .format(descriptor))
+            raise Error(f"can't create source from descriptor {descriptor}")
 
         return Source(pointer)
 
@@ -57,8 +56,7 @@ def new_from_file(filename):
 
         pointer = vips_lib.vips_source_new_from_file(_to_bytes(filename))
         if pointer == ffi.NULL:
-            raise Error("can't create source from filename {0}"
-                        .format(filename))
+            raise Error(f"can't create source from filename {filename}")
 
         return Source(pointer)
 
diff --git a/pyvips/vtarget.py b/pyvips/vtarget.py
index 9eecfdf..10de359 100644
--- a/pyvips/vtarget.py
+++ b/pyvips/vtarget.py
@@ -36,8 +36,8 @@ def new_to_descriptor(descriptor):
         # targets are mutable, so we can't use the cache
         pointer = vips_lib.vips_target_new_to_descriptor(descriptor)
         if pointer == ffi.NULL:
-            raise Error("can't create output target from descriptor {0}"
-                        .format(descriptor))
+            raise Error(f"can't create output target from descriptor "
+                        f'{descriptor}')
 
         return Target(pointer)
 
@@ -57,8 +57,7 @@ def new_to_file(filename):
 
         pointer = vips_lib.vips_target_new_to_file(_to_bytes(filename))
         if pointer == ffi.NULL:
-            raise Error("can't create output target from filename {0}"
-                        .format(filename))
+            raise Error(f"can't create output target from filename {filename}")
 
         return Target(pointer)
 
diff --git a/setup.py b/setup.py
index 2bebdae..331453c 100644
--- a/setup.py
+++ b/setup.py
@@ -18,5 +18,5 @@
 try:
     setup(cffi_modules=['pyvips/pyvips_build.py:ffibuilder'])
 except Exception as e:
-    print('Falling back to ABI mode. Details: {0}'.format(e))
+    print(f'Falling back to ABI mode. Details: {e}')
     setup()
diff --git a/tests/helpers/helpers.py b/tests/helpers/helpers.py
index d7f14fd..be35059 100644
--- a/tests/helpers/helpers.py
+++ b/tests/helpers/helpers.py
@@ -74,14 +74,14 @@ def run_fn2(fn, x, y):
 
 # test a pair of things which can be lists for approx. equality
 def assert_almost_equal_objects(a, b, threshold=0.0001, msg=''):
-    # print 'assertAlmostEqualObjects %s = %s' % (a, b)
+    # print(f'assertAlmostEqualObjects {a} = {b}')
     assert all([pytest.approx(x, abs=threshold) == y
                 for x, y in zip_expand(a, b)]), msg
 
 
 # test a pair of things which can be lists for equality
 def assert_equal_objects(a, b, msg=''):
-    # print 'assertEqualObjects %s = %s' % (a, b)
+    # print(f'assertEqualObjects {a} = {b}')
     assert all([x == y for x, y in zip_expand(a, b)]), msg