diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 7c983aa6..c937decb 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -27,14 +27,12 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        python-version: ["2.7", "3.5", "3.6", "3.8", "3.9", "3.10"]
+        python-version: ["3.6", "3.8", "3.9", "3.10"]
         include:
-          - {os: macos-latest, python-version: '2.7'}
-          - {os: macos-latest, python-version: '3.9'}
+          - {os: macos-latest, python-version: '3.6'}
+          - {os: macos-latest, python-version: '3.10'}
           - {os: windows-latest, python-version: '3.7'}
           - {os: windows-latest, python-version: '3.9'}
-        exclude:
-          - {os: ubuntu-latest, python-version: '3.7'}
 
     steps:
     - uses: actions/checkout@v2
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 918385c8..5fd02e9f 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -15,7 +15,6 @@ repos:
   - id: requirements-txt-fixer
   - id: debug-statements
   - id: end-of-file-fixer
-  - id: fix-encoding-pragma
 
 - repo: https://github.com/PyCQA/isort
   rev: 5.10.1
@@ -31,12 +30,12 @@ repos:
   rev: v1.20.0
   hooks:
   - id: setup-cfg-fmt
-    args: [--max-py-version=3.10, --min-py3-version=3.5]
 
 - repo: https://github.com/asottile/pyupgrade
   rev: v2.29.1
   hooks:
   - id: pyupgrade
+    args: ["--py36-plus"]
 
 - repo: https://github.com/mgedmin/check-manifest
   rev: "0.47"
@@ -55,7 +54,7 @@ repos:
   hooks:
   - id: mypy
     files: src
-    additional_dependencies: [attrs==19.3.0, types-deprecated]
+    additional_dependencies: [attrs==21.2.0, types-deprecated]
 
 - repo: https://github.com/codespell-project/codespell
   rev: v2.1.0
diff --git a/admin/dump_pdgid_to_lhcb.py b/admin/dump_pdgid_to_lhcb.py
index 206fe1a2..d5a9a17b 100755
--- a/admin/dump_pdgid_to_lhcb.py
+++ b/admin/dump_pdgid_to_lhcb.py
@@ -1,5 +1,4 @@
 #!/usr/bin/env python
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/noxfile.py b/noxfile.py
index a430d74f..f17b0f5b 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 from pathlib import Path
 
 import nox
diff --git a/setup.cfg b/setup.cfg
index 999e7f24..4e3bc2ae 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -17,10 +17,8 @@ classifiers =
     License :: OSI Approved :: BSD License
     Operating System :: OS Independent
     Programming Language :: Python
-    Programming Language :: Python :: 2
-    Programming Language :: Python :: 2.7
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.5
+    Programming Language :: Python :: 3 :: Only
     Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
@@ -42,11 +40,9 @@ install_requires =
     attrs>=19.2
     deprecated
     hepunits>=2.0.0
-    enum34>=1.1;python_version<"3.4"
     importlib-resources>=2.0;python_version<"3.9"
-    typing>=3.7;python_version<"3.5"
     typing-extensions;python_version<"3.8"
-python_requires = >=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*
+python_requires = >=3.6
 include_package_data = True
 package_dir =
     =src
@@ -57,22 +53,22 @@ where = src
 [options.extras_require]
 all =
     check-manifest>=0.42
-    pytest
+    pandas
+    pytest>=6
     pytest-benchmark
     tabulate
-    pandas;python_version>"3.4"
 dev =
     check-manifest>=0.42
-    pytest
+    pandas
+    pytest>=6
     pytest-benchmark
     tabulate
-    pandas;python_version>"3.4"
 test =
-    pytest
+    pandas
+    pytest>=6
     pytest-benchmark
     pytest-cov
     tabulate
-    pandas;python_version>"3.4"
 
 [options.package_data]
 * = *.csv, *.fwf, *.mcd, *.py.typed
@@ -90,5 +86,5 @@ filterwarnings =
 
 [flake8]
 max-complexity = 24
-ignore = E203, E231, E501, E722, W503, B950, E402, B904
+ignore = E203, E231, E501, E722, W503, B950, E402
 select = C,E,F,W,B,B9
diff --git a/setup.py b/setup.py
index 1b95755a..7afd1c56 100644
--- a/setup.py
+++ b/setup.py
@@ -1,5 +1,4 @@
 #!/usr/bin/env python
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/src/particle/__init__.py b/src/particle/__init__.py
index a0fdd6bf..06eb370f 100644
--- a/src/particle/__init__.py
+++ b/src/particle/__init__.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import
 
 import sys
 from typing import Tuple
diff --git a/src/particle/__main__.py b/src/particle/__main__.py
index a3be94ed..935da28b 100644
--- a/src/particle/__main__.py
+++ b/src/particle/__main__.py
@@ -1,11 +1,9 @@
 #!/usr/bin/env python
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import, print_function
 
 import argparse
 import sys
@@ -25,7 +23,7 @@ def main():
     parser.add_argument(
         "--version",
         action="version",
-        version="%(prog)s {version}".format(version=__version__),
+        version=f"%(prog)s {__version__}",
     )
 
     subparsers = parser.add_subparsers(help="Subcommands")
diff --git a/src/particle/converters/__init__.py b/src/particle/converters/__init__.py
index 56d50df7..18d3e40b 100644
--- a/src/particle/converters/__init__.py
+++ b/src/particle/converters/__init__.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import
 
 from typing import Tuple
 
diff --git a/src/particle/converters/bimap.py b/src/particle/converters/bimap.py
index fe7d19ab..dc5f754e 100644
--- a/src/particle/converters/bimap.py
+++ b/src/particle/converters/bimap.py
@@ -1,19 +1,11 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import
-
-try:
-    # for Python 3
-    from collections.abc import Mapping
-except ImportError:
-    # for Python 2.7
-    from collections import Mapping
 
 import csv
+from collections.abc import Mapping
 from typing import (
     Any,
     Callable,
@@ -88,7 +80,7 @@ def __init__(self, class_A, class_B, converters=(int, int), filename=None):
         name_B = self.class_B.__name__.upper()
 
         if filename is None:
-            filename = "{a}_to_{b}.csv".format(a=name_A.lower(), b=name_B.lower())
+            filename = f"{name_A.lower()}_to_{name_B.lower()}.csv"
             file_object = data.basepath.joinpath(filename).open()
         elif isinstance(filename, HasRead):
             file_object = filename
diff --git a/src/particle/converters/evtgen.py b/src/particle/converters/evtgen.py
index 4508c264..01db64d7 100644
--- a/src/particle/converters/evtgen.py
+++ b/src/particle/converters/evtgen.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import
 
 from .. import data
 from ..pdgid import PDGID
diff --git a/src/particle/converters/geant.py b/src/particle/converters/geant.py
index c7dc8569..3b06f977 100644
--- a/src/particle/converters/geant.py
+++ b/src/particle/converters/geant.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import
 
 from ..geant import Geant3ID
 from ..pdgid import PDGID
diff --git a/src/particle/converters/pythia.py b/src/particle/converters/pythia.py
index 8ee360f5..e4d24440 100644
--- a/src/particle/converters/pythia.py
+++ b/src/particle/converters/pythia.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import
 
 from ..pdgid import PDGID
 from ..pythia import PythiaID
diff --git a/src/particle/data/__init__.py b/src/particle/data/__init__.py
index 75be5f6d..6bb2ba85 100644
--- a/src/particle/data/__init__.py
+++ b/src/particle/data/__init__.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/src/particle/exceptions.py b/src/particle/exceptions.py
index e35ac4f8..489de26d 100644
--- a/src/particle/exceptions.py
+++ b/src/particle/exceptions.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/src/particle/geant/__init__.py b/src/particle/geant/__init__.py
index 7aa733da..a9ffdbc6 100644
--- a/src/particle/geant/__init__.py
+++ b/src/particle/geant/__init__.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import
 
 from typing import Tuple
 
diff --git a/src/particle/geant/geant3id.py b/src/particle/geant/geant3id.py
index bc804a28..9727a9f5 100644
--- a/src/particle/geant/geant3id.py
+++ b/src/particle/geant/geant3id.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
@@ -13,7 +12,6 @@
 follows the PDG rules, hence uses the standard PDG IDs.
 """
 
-from __future__ import absolute_import
 
 import csv
 
@@ -55,9 +53,7 @@ def from_pdgid(cls, pdgid):
         for k, v in _bimap.items():
             if v == pdgid:
                 return cls(k)
-        raise MatchingIDNotFound(
-            "Non-existent Geant3ID for input PDGID {} !".format(pdgid)
-        )
+        raise MatchingIDNotFound(f"Non-existent Geant3ID for input PDGID {pdgid} !")
 
     def to_pdgid(self):
         # type: () -> PDGID
@@ -65,7 +61,7 @@ def to_pdgid(self):
 
     def __repr__(self):
         # type: () -> str
-        return "<Geant3ID: {:d}>".format(int(self))
+        return f"<Geant3ID: {int(self):d}>"
 
     def __str__(self):
         # type: () -> str
diff --git a/src/particle/lhcb/__init__.py b/src/particle/lhcb/__init__.py
index d38940ed..a61360d2 100644
--- a/src/particle/lhcb/__init__.py
+++ b/src/particle/lhcb/__init__.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import
 
 from typing import Tuple
 
diff --git a/src/particle/lhcb/converters/__init__.py b/src/particle/lhcb/converters/__init__.py
index 9bf45bf2..bb7194c0 100644
--- a/src/particle/lhcb/converters/__init__.py
+++ b/src/particle/lhcb/converters/__init__.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import
 
 from typing import Tuple
 
diff --git a/src/particle/lhcb/converters/lhcb.py b/src/particle/lhcb/converters/lhcb.py
index fc96baf4..45853481 100644
--- a/src/particle/lhcb/converters/lhcb.py
+++ b/src/particle/lhcb/converters/lhcb.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import
 
 from ...converters.bimap import BiMap
 from ...pdgid import PDGID
diff --git a/src/particle/lhcb/data/__init__.py b/src/particle/lhcb/data/__init__.py
index bdce3bec..9cb3b019 100644
--- a/src/particle/lhcb/data/__init__.py
+++ b/src/particle/lhcb/data/__init__.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/src/particle/lhcb/utils.py b/src/particle/lhcb/utils.py
index f999f821..8683670a 100644
--- a/src/particle/lhcb/utils.py
+++ b/src/particle/lhcb/utils.py
@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 from ..particle import Particle
 from .converters import LHCbName2PDGIDBiMap
 
diff --git a/src/particle/particle/__init__.py b/src/particle/particle/__init__.py
index 91531fb0..31bb057c 100644
--- a/src/particle/particle/__init__.py
+++ b/src/particle/particle/__init__.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import
 
 from typing import Tuple
 
diff --git a/src/particle/particle/convert.py b/src/particle/particle/convert.py
index 8a0dba0c..cf6fe87c 100644
--- a/src/particle/particle/convert.py
+++ b/src/particle/particle/convert.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
@@ -53,6 +52,7 @@
 
 import os
 from datetime import date
+from io import StringIO
 from typing import (
     Any,
     Callable,
@@ -68,14 +68,6 @@
 import numpy as np
 import pandas as pd
 
-try:
-    from io import StringIO
-except ImportError:  # Python2 workaround, could also use six
-    try:
-        from cStringIO import StringIO  # type: ignore
-    except ImportError:
-        from StringIO import StringIO  # type: ignore
-
 from .. import data
 from ..pdgid import PDGID, is_baryon
 from .enums import (
@@ -346,11 +338,11 @@ def get_from_pdg_mcd(filename):
             print("DUPLICATES:\n", nar[duplicated_ids])
         assert (
             nar[duplicated_ids].shape[0] == 0
-        ), "Duplicate entries found in {} !".format(filename)
+        ), f"Duplicate entries found in {filename} !"
 
     ds_list = []
     for i in range(4):
-        name = "ID{}".format(i + 1)
+        name = f"ID{i + 1}"
         d = nar[~pd.isna(nar[name])].copy()
         d["ID"] = d[name].astype(int)
         nc = d.NameCharge.str.split(expand=True)
diff --git a/src/particle/particle/enums.py b/src/particle/particle/enums.py
index 6e9a12a8..43a23970 100644
--- a/src/particle/particle/enums.py
+++ b/src/particle/particle/enums.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/src/particle/particle/kinematics.py b/src/particle/particle/kinematics.py
index 29e7b6a6..043464b1 100644
--- a/src/particle/particle/kinematics.py
+++ b/src/particle/particle/kinematics.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
@@ -8,7 +7,6 @@
 Functions relevant to particle kinematics.
 """
 
-from __future__ import absolute_import, division, print_function
 
 from hepunits.constants import hbar
 from hepunits.units import MeV, ns
@@ -52,7 +50,7 @@ def width_to_lifetime(Gamma):
     """
 
     if Gamma < 0.0:
-        raise ValueError("Input provided, {} <= 0!".format(Gamma))
+        raise ValueError(f"Input provided, {Gamma} <= 0!")
     elif Gamma == 0:
         return float("inf")
 
@@ -99,7 +97,7 @@ def lifetime_to_width(tau):
     """
 
     if tau < 0:
-        raise ValueError("Input provided, {} <= 0!".format(tau))
+        raise ValueError(f"Input provided, {tau} <= 0!")
     elif tau == 0:
         return float("inf")
 
diff --git a/src/particle/particle/literals.py b/src/particle/particle/literals.py
index ecdb9fb5..2a83cc2f 100644
--- a/src/particle/particle/literals.py
+++ b/src/particle/particle/literals.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/src/particle/particle/particle.py b/src/particle/particle/particle.py
index d11eb2ab..3a93b444 100644
--- a/src/particle/particle/particle.py
+++ b/src/particle/particle/particle.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import, division, print_function
 
 # Python standard library
 import csv
@@ -87,7 +85,7 @@ def _none_or_positive_converter(value):
 
 @total_ordering
 @attr.s(slots=True, eq=False, order=False, repr=False)
-class Particle(object):
+class Particle:
     """
     The Particle object class. Hold a series of properties for a particle.
 
@@ -293,7 +291,7 @@ def to_list(
         n_rows=-1,  # type: int
         filter_fn=None,  # type: Optional[Callable[[Particle], bool]]
         particle=None,  # type: Optional[bool]
-        **search_terms  # type: Any
+        **search_terms,  # type: Any
     ):
         # type: (...) -> List[List[Union[bool, int, str, float]]]
         """
@@ -419,7 +417,7 @@ def to_list(
 
         # Apply a filter, if specified
         if filter_fn is not None:
-            tbl_all = cls.findall(filter_fn, particle, **search_terms)
+            tbl_all = cls.findall(filter_fn, particle=particle, **search_terms)
 
         # In any case, only keep a given number of rows?
         if n_rows >= 0:
@@ -576,9 +574,7 @@ def load_table(cls, filename=None, append=False, _name=None):
             return
         elif isinstance(filename, HasRead):
             tmp_name = _name or filename.name
-            cls._table_names.append(
-                tmp_name or "{!r} {}".format(filename, len(cls._table_names))
-            )
+            cls._table_names.append(tmp_name or f"{filename!r} {len(cls._table_names)}")
             open_file = filename
         elif isinstance(filename, HasOpen):
             cls._table_names.append(str(filename))
@@ -857,7 +853,7 @@ def _width_or_lifetime(self):
         elif self.width == 0:
             return "Width = 0.0 MeV"
         elif self.width_lower is None or self.width_upper is None:
-            return "Width < {width} MeV".format(width=self.width)
+            return f"Width < {self.width} MeV"
         elif (
             self.width < 0.05
         ):  # corresponds to a lifetime of approximately 1.3e-20 seconds
@@ -981,9 +977,9 @@ def describe(self):
         )
 
         if self.spin_type != SpinType.Unknown:
-            val += "    SpinType: {self.spin_type!s}\n".format(self=self)
+            val += f"    SpinType: {self.spin_type!s}\n"
         if self.quarks:
-            val += "    Quarks: {self.quarks}\n".format(self=self)
+            val += f"    Quarks: {self.quarks}\n"
         val += "    Antiparticle name: {inv_self.name} (antiparticle status: {self.anti_flag.name})".format(
             inv_self=self.invert(), self=self
         )
@@ -1028,7 +1024,7 @@ def from_pdgid(cls, value):
             If no matching PDG ID is found in the loaded data table(s).
         """
         if not is_valid(value):
-            raise InvalidParticle("Input PDGID {} is invalid!".format(value))
+            raise InvalidParticle(f"Input PDGID {value} is invalid!")
 
         if not cls.table_loaded():
             cls.load_table()
@@ -1039,7 +1035,7 @@ def from_pdgid(cls, value):
             return cls._hash_table[int(value)]
         except KeyError:
             raise ParticleNotFound(  # noqa: B904  <- use from None when Python 2 is dropped
-                "Could not find PDGID {}".format(value)
+                f"Could not find PDGID {value}"
             )
 
     @classmethod
@@ -1060,7 +1056,7 @@ def from_name(cls, name):
             return particle
         except ValueError:
             raise ParticleNotFound(  # noqa: B904  <- use from None when Python 2 is dropped
-                'Could not find name "{}"'.format(name)
+                f'Could not find name "{name}"'
             )
 
     @classmethod
@@ -1082,8 +1078,9 @@ def from_evtgen_name(cls, name):
     def finditer(
         cls,
         filter_fn=None,  # type: Optional[Callable[[Particle], bool]]
+        *,
         particle=None,  # type: Optional[bool]
-        **search_terms  # type: Any
+        **search_terms,  # type: Any
     ):
         # type: (...) -> Iterator[Particle]
         """
@@ -1124,9 +1121,6 @@ def finditer(
         See also ``findall``, which returns the same thing, but as a list.
         """
 
-        # Note that particle can be called by position to keep compatibility with Python 2, but that behavior should
-        # not be used and will be removed when support for Python 2.7 is dropped.
-
         # Filter out values
         for item in cls.all():
             # At this point, continue if a match fails
@@ -1180,8 +1174,9 @@ def finditer(
     def findall(
         cls,
         filter_fn=None,  # type: Optional[Callable[[Particle], bool]]
+        *,
         particle=None,  # type: Optional[bool]
-        **search_terms  # type: Any
+        **search_terms,  # type: Any
     ):
         # type: (...) -> List[Particle]
 
@@ -1258,7 +1253,7 @@ def find(cls, *args, **search_terms):
             return results[0]
         elif len(results) == 0:
             raise ParticleNotFound(
-                "Did not find particle matching query: {}".format(search_terms)
+                f"Did not find particle matching query: {search_terms}"
             )
         else:
             raise RuntimeError("Found too many particles")
@@ -1271,7 +1266,7 @@ def from_string(cls, name):
         if matches:
             return matches[0]
         else:
-            raise ParticleNotFound("{} not found in particle table".format(name))
+            raise ParticleNotFound(f"{name} not found in particle table")
 
     @classmethod
     def from_string_list(cls, name):
@@ -1348,9 +1343,7 @@ def _from_group_dict_list(cls, mat):
             vals = cls.findall(name=lambda x: name in x, **kw)
 
         if not vals:
-            raise ParticleNotFound(
-                "Could not find particle {} or {}".format(maxname, name)
-            )
+            raise ParticleNotFound(f"Could not find particle {maxname} or {name}")
 
         if len(vals) > 1 and mat["mass"] is not None:
             vals = [val for val in vals if mat["mass"] in val.latex_name]
diff --git a/src/particle/particle/regex.py b/src/particle/particle/regex.py
index 25cf54fe..f4eba936 100644
--- a/src/particle/particle/regex.py
+++ b/src/particle/particle/regex.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/src/particle/particle/utilities.py b/src/particle/particle/utilities.py
index 6ca945c8..0124f566 100644
--- a/src/particle/particle/utilities.py
+++ b/src/particle/particle/utilities.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
@@ -6,7 +5,6 @@
 
 import math
 import re
-import sys
 import unicodedata
 from typing import Optional
 
@@ -67,13 +65,13 @@ def str_with_unc(value, upper, lower=None):
     # This is normal notation
     if -3 < value_digits < 6:
         if error_digits < 0:
-            fsv = fse = ".{}f".format(-error_digits)
+            fsv = fse = f".{-error_digits}f"
         else:
             fsv = fse = ".0f"
 
     # This is scientific notation - a little odd, but better than the other options.
     else:
-        fsv = ".{}e".format(abs(error_digits - value_digits))
+        fsv = f".{abs(error_digits - value_digits)}e"
         pure_error_digits = int(math.floor(math.log10(error)))
 
         fse = ".0e" if error_digits == pure_error_digits else ".1e"
@@ -84,12 +82,7 @@ def str_with_unc(value, upper, lower=None):
             value=value, upper=upper, lower=lower, fsv=fsv, fse=fse
         )
 
-    # Only bother with unicode if this is Python 3.
-    pm = u"±" if sys.version_info >= (3,) else "+/-"
-
-    return "{value:{fsv}} {pm} {upper:{fse}}".format(
-        value=value, pm=pm, upper=upper, fsv=fsv, fse=fse
-    )
+    return f"{value:{fsv}} ± {upper:{fse}}"
 
 
 # List of greek letter names as used in Unicode (see unicodedata package)
@@ -165,7 +158,7 @@ def latex_name_unicode(name):
     if "ambda" in name:
         name = name.replace("ambda", "amda")
     for gl in _list_name_greek_letters:
-        name = name.replace(r"\{}".format(gl), greek_letter_name_to_unicode(gl))
+        name = name.replace(fr"\{gl}", greek_letter_name_to_unicode(gl))
     return name
 
 
diff --git a/src/particle/pdgid/__init__.py b/src/particle/pdgid/__init__.py
index e216fc28..4c9164d7 100644
--- a/src/particle/pdgid/__init__.py
+++ b/src/particle/pdgid/__init__.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
@@ -59,7 +58,6 @@
 
 """
 
-from __future__ import absolute_import
 
 from typing import Tuple
 
diff --git a/src/particle/pdgid/functions.py b/src/particle/pdgid/functions.py
index c8bf6e59..ec2b0ef4 100644
--- a/src/particle/pdgid/functions.py
+++ b/src/particle/pdgid/functions.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
@@ -24,7 +23,6 @@
 - HepPDT and HepPID versions 3.04.01.
 """
 
-from __future__ import absolute_import, division, print_function
 
 from enum import IntEnum
 from typing import Optional, SupportsInt
diff --git a/src/particle/pdgid/literals.py b/src/particle/pdgid/literals.py
index 8e0aab10..c8b33e6e 100644
--- a/src/particle/pdgid/literals.py
+++ b/src/particle/pdgid/literals.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
@@ -38,8 +37,7 @@
 
 
 __doc = "".join(
-    "  {item!s} = PDGID({pdgid})\n".format(item=item, pdgid=common_particles[item])
-    for item in common_particles
+    f"  {item!s} = PDGID({common_particles[item]})\n" for item in common_particles
 )
 __doc__ = __doc__.format(__doc)
 
diff --git a/src/particle/pdgid/pdgid.py b/src/particle/pdgid/pdgid.py
index 60a785da..b3e92cf4 100644
--- a/src/particle/pdgid/pdgid.py
+++ b/src/particle/pdgid/pdgid.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
@@ -10,7 +9,6 @@
 All methods of HepPID are implemented in a Pythonic version, see the functions module.
 """
 
-from __future__ import absolute_import
 
 from inspect import isfunction
 
@@ -58,7 +56,7 @@ def info(self):
         Print all PDGID properties one per line, for easy inspection.
         """
         return "".join(
-            "{item:14} {value}\n".format(item=item, value=getattr(self, item))
+            f"{item:14} {getattr(self, item)}\n"
             for item in _fnames
             if item != "is_composite_quark_or_lepton"
         )
@@ -135,4 +133,4 @@ def info(self):
 for _n in _fnames:
     assert _n in dir(
         PDGID
-    ), "{} missing from PDGID class! Update the list in pdgid.py".format(_n)
+    ), f"{_n} missing from PDGID class! Update the list in pdgid.py"
diff --git a/src/particle/pythia/__init__.py b/src/particle/pythia/__init__.py
index 10ea60e0..a433ddd9 100644
--- a/src/particle/pythia/__init__.py
+++ b/src/particle/pythia/__init__.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import
 
 from typing import Tuple
 
diff --git a/src/particle/pythia/pythiaid.py b/src/particle/pythia/pythiaid.py
index d958b8be..3ed31262 100644
--- a/src/particle/pythia/pythiaid.py
+++ b/src/particle/pythia/pythiaid.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
@@ -8,7 +7,6 @@
 Class representing a Pythia ID.
 """
 
-from __future__ import absolute_import
 
 import csv
 
@@ -50,9 +48,7 @@ def from_pdgid(cls, pdgid):
         for k, v in _bimap.items():
             if v == pdgid:
                 return cls(k)
-        raise MatchingIDNotFound(
-            "Non-existent PythiaID for input PDGID {} !".format(pdgid)
-        )
+        raise MatchingIDNotFound(f"Non-existent PythiaID for input PDGID {pdgid} !")
 
     def to_pdgid(self):
         # type: () -> PDGID
@@ -60,7 +56,7 @@ def to_pdgid(self):
 
     def __repr__(self):
         # type: () -> str
-        return "<PythiaID: {:d}>".format(int(self))
+        return f"<PythiaID: {int(self):d}>"
 
     def __str__(self):
         # type: () -> str
diff --git a/src/particle/shared_literals.py b/src/particle/shared_literals.py
index a10f73d0..97b68bba 100644
--- a/src/particle/shared_literals.py
+++ b/src/particle/shared_literals.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
@@ -11,7 +10,6 @@
 See the particle.literals and the pdgid.literals submodules for the actually exposed aliases.
 """
 
-from __future__ import absolute_import
 
 from .particle import Particle
 
diff --git a/src/particle/typing.py b/src/particle/typing.py
index 37f18e3a..1913df83 100644
--- a/src/particle/typing.py
+++ b/src/particle/typing.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import, division, print_function
 
 import sys
 
diff --git a/tests/__init__.py b/tests/__init__.py
index f4bad91d..a47ee414 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/tests/conftest.py b/tests/conftest.py
index dac6303b..8f831c90 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/tests/converters/__init__.py b/tests/converters/__init__.py
index f4bad91d..a47ee414 100644
--- a/tests/converters/__init__.py
+++ b/tests/converters/__init__.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/tests/converters/test_maps.py b/tests/converters/test_maps.py
index a02b7dc6..adbcfd95 100644
--- a/tests/converters/test_maps.py
+++ b/tests/converters/test_maps.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/tests/geant/__init__.py b/tests/geant/__init__.py
index f4bad91d..a47ee414 100644
--- a/tests/geant/__init__.py
+++ b/tests/geant/__init__.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/tests/geant/test_geant3id.py b/tests/geant/test_geant3id.py
index 53793356..427de0b8 100644
--- a/tests/geant/test_geant3id.py
+++ b/tests/geant/test_geant3id.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/tests/lhcb/test_lhcb_name.py b/tests/lhcb/test_lhcb_name.py
index 6e5945d1..c157eaf7 100644
--- a/tests/lhcb/test_lhcb_name.py
+++ b/tests/lhcb/test_lhcb_name.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/tests/particle/__init__.py b/tests/particle/__init__.py
index f4bad91d..a47ee414 100644
--- a/tests/particle/__init__.py
+++ b/tests/particle/__init__.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/tests/particle/test_convert.py b/tests/particle/test_convert.py
index 0cf6b073..550f2b11 100644
--- a/tests/particle/test_convert.py
+++ b/tests/particle/test_convert.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
@@ -9,13 +8,9 @@
 # Requires pandas
 pd = pytest.importorskip("pandas")
 
-from particle.particle.convert import get_from_pdg_mcd
-
-try:
-    from pathlib2 import Path
-except ImportError:
-    from pathlib import Path
+from pathlib import Path
 
+from particle.particle.convert import get_from_pdg_mcd
 
 DIR = Path(__file__).parent.resolve()
 
diff --git a/tests/particle/test_decfilenames.py b/tests/particle/test_decfilenames.py
index aebac12c..f3ae6516 100644
--- a/tests/particle/test_decfilenames.py
+++ b/tests/particle/test_decfilenames.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import, division, print_function
 
 from particle.particle import Particle, ParticleNotFound
 
diff --git a/tests/particle/test_enums.py b/tests/particle/test_enums.py
index 2fe57146..a7711e20 100644
--- a/tests/particle/test_enums.py
+++ b/tests/particle/test_enums.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import, division, print_function
 
 from particle.particle.enums import Charge, SpinType
 
diff --git a/tests/particle/test_generation.py b/tests/particle/test_generation.py
index 02d7c852..ce2d26cf 100644
--- a/tests/particle/test_generation.py
+++ b/tests/particle/test_generation.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/tests/particle/test_kinematics.py b/tests/particle/test_kinematics.py
index 51bc3a0b..2267a522 100644
--- a/tests/particle/test_kinematics.py
+++ b/tests/particle/test_kinematics.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/tests/particle/test_literals.py b/tests/particle/test_literals.py
index b391dd17..4ed69281 100644
--- a/tests/particle/test_literals.py
+++ b/tests/particle/test_literals.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import division
 
 from particle import literals as lp
 
diff --git a/tests/particle/test_particle.py b/tests/particle/test_particle.py
index 2afb103d..2af72ef8 100644
--- a/tests/particle/test_particle.py
+++ b/tests/particle/test_particle.py
@@ -1,12 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import, division, print_function
-
-import sys
 
 import pytest
 from hepunits import meter, second
@@ -313,14 +309,14 @@ def test_C_consistency():
     # Test print-out of zero width values
     [22, "Width = 0.0 MeV"],  # photon
     # Test print-out of symmetric width errors
-    [413, u"Width = 0.0834 ± 0.0018 MeV"],  # D*(2010)+
-    [443, u"Width = 0.0926 ± 0.0017 MeV"],  # J/psi
+    [413, "Width = 0.0834 ± 0.0018 MeV"],  # D*(2010)+
+    [443, "Width = 0.0926 ± 0.0017 MeV"],  # J/psi
     # Test print-out of asymmetric width errors
     [4222, "Width = 1.89 + 0.09 - 0.18 MeV"],  # Sigma_c(2455)++
-    [23, u"Width = 2495.2 ± 2.3 MeV"],  # H0
+    [23, "Width = 2495.2 ± 2.3 MeV"],  # H0
     # Test print-out of symmetric lifetime errors
-    [5332, u"Lifetime = 1.65e-03 + 1.8e-04 - 1.8e-04 ns"],  # Omega_b-
-    [211, u"Lifetime = 26.033 ± 0.005 ns"],  # pion
+    [5332, "Lifetime = 1.65e-03 + 1.8e-04 - 1.8e-04 ns"],  # Omega_b-
+    [211, "Lifetime = 26.033 ± 0.005 ns"],  # pion
     # Test print-out of asymmetric lifetime errors
     [4332, "Lifetime = 2.7e-04 + 3e-05 - 3e-05 ns"],  # Omega_c^0
     # Test particles with at present an upper limit on their width
@@ -330,9 +326,6 @@ def test_C_consistency():
     [4212, "Width < 4.6 MeV"],  # Sigma(c)(2455)+
     [4214, "Width < 17.0 MeV"],  # Sigma(c)(2520)+
 )
-if sys.version_info < (3, 0):
-    for i, pair_vals in enumerate(checklist_describe):
-        checklist_describe[i][1] = pair_vals[1].replace(u"±", u"+/-")
 
 
 @pytest.mark.parametrize("pid,description", checklist_describe)
@@ -405,7 +398,6 @@ def test_all_particles_are_loaded():
 )
 
 
-@pytest.mark.skipif(sys.version_info < (3, 0), reason="Requires Python 3")
 @pytest.mark.parametrize("pid,html_name", checklist_html_name)
 def test_html_name(pid, html_name):
     particle = Particle.from_pdgid(pid)
diff --git a/tests/particle/test_performance.py b/tests/particle/test_performance.py
index 68f3cc26..40b0a8f9 100644
--- a/tests/particle/test_performance.py
+++ b/tests/particle/test_performance.py
@@ -1,5 +1,3 @@
-# -*- coding: utf-8 -*-
-
 from particle import Particle, data
 
 
diff --git a/tests/particle/test_utilities.py b/tests/particle/test_utilities.py
index 3c5f251a..8386efa2 100644
--- a/tests/particle/test_utilities.py
+++ b/tests/particle/test_utilities.py
@@ -1,35 +1,29 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-import sys
-
 import pytest
 
 from particle.particle.utilities import str_with_unc
 
 possibilities = (
-    (1.234567, 0.01, None, u"1.235 ± 0.010"),
-    (1.234567e-9, 0.01e-9, None, u"1.235e-09 ± 1.0e-11"),
-    (1.234567e9, 0.04e9, None, u"1.23e+09 ± 4e+07"),
-    (0.001, 0.00001, None, u"1.000e-03 ± 1.0e-05"),
-    (0.00099, 0.00001, None, u"9.90e-04 ± 1.0e-05"),
-    (99, 0.24, None, u"99.00 ± 0.24"),
-    (100, 0.25, None, u"100.0 ± 0.2"),
-    (101, 0.26, None, u"101.0 ± 0.3"),
-    (0.00001231, 0.000002, 0.000004, u"1.23e-05 + 2.0e-06 - 4.0e-06"),
-    (1234.5, 0.03, 0.03, u"1234.50 ± 0.03"),
-    (1234.5, 5, 5, u"1234 ± 5"),
-    (1234.5, 2, 2, u"1234.5 ± 2.0"),
+    (1.234567, 0.01, None, "1.235 ± 0.010"),
+    (1.234567e-9, 0.01e-9, None, "1.235e-09 ± 1.0e-11"),
+    (1.234567e9, 0.04e9, None, "1.23e+09 ± 4e+07"),
+    (0.001, 0.00001, None, "1.000e-03 ± 1.0e-05"),
+    (0.00099, 0.00001, None, "9.90e-04 ± 1.0e-05"),
+    (99, 0.24, None, "99.00 ± 0.24"),
+    (100, 0.25, None, "100.0 ± 0.2"),
+    (101, 0.26, None, "101.0 ± 0.3"),
+    (0.00001231, 0.000002, 0.000004, "1.23e-05 + 2.0e-06 - 4.0e-06"),
+    (1234.5, 0.03, 0.03, "1234.50 ± 0.03"),
+    (1234.5, 5, 5, "1234 ± 5"),
+    (1234.5, 2, 2, "1234.5 ± 2.0"),
 )
 
 
 @pytest.mark.parametrize("value,err_u,err_l,test_str", possibilities)
 def test_unc_printout(value, err_u, err_l, test_str):
 
-    if sys.version_info < (3, 0):
-        test_str = test_str.replace(u"±", u"+/-")
-
     assert str_with_unc(value, err_u, err_l) == test_str
diff --git a/tests/pdgid/__init__.py b/tests/pdgid/__init__.py
index f4bad91d..a47ee414 100644
--- a/tests/pdgid/__init__.py
+++ b/tests/pdgid/__init__.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/tests/pdgid/test_functions.py b/tests/pdgid/test_functions.py
index f57d2a58..d646cb88 100644
--- a/tests/pdgid/test_functions.py
+++ b/tests/pdgid/test_functions.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import absolute_import, division, print_function
 
 from particle.pdgid import (
     A,
diff --git a/tests/pdgid/test_literals.py b/tests/pdgid/test_literals.py
index b616f627..a6c3f618 100644
--- a/tests/pdgid/test_literals.py
+++ b/tests/pdgid/test_literals.py
@@ -1,10 +1,8 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
 # or https://github.com/scikit-hep/particle for details.
 
-from __future__ import division
 
 from particle.pdgid import literals as lid
 
diff --git a/tests/pdgid/test_pdgid.py b/tests/pdgid/test_pdgid.py
index a105eb95..80f7143f 100644
--- a/tests/pdgid/test_pdgid.py
+++ b/tests/pdgid/test_pdgid.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/tests/pythia/__init__.py b/tests/pythia/__init__.py
index f4bad91d..a47ee414 100644
--- a/tests/pythia/__init__.py
+++ b/tests/pythia/__init__.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/tests/pythia/test_pythiaid.py b/tests/pythia/test_pythiaid.py
index 249dfb8f..e36dbcff 100644
--- a/tests/pythia/test_pythiaid.py
+++ b/tests/pythia/test_pythiaid.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE
diff --git a/tests/test_package.py b/tests/test_package.py
index 0757ef25..ec935441 100644
--- a/tests/test_package.py
+++ b/tests/test_package.py
@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 # Copyright (c) 2018-2021, Eduardo Rodrigues and Henry Schreiner.
 #
 # Distributed under the 3-clause BSD license, see accompanying file LICENSE