diff --git a/.git-blame-ignore-revs b/.git-blame-ignore-revs
new file mode 100644
index 0000000..4b73daf
--- /dev/null
+++ b/.git-blame-ignore-revs
@@ -0,0 +1,2 @@
+# trivial: apply pyupgrade (#58937)
+caa40e7e771b41bd1d164341a2e7f40689cbe4ba
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
new file mode 100644
index 0000000..dcca49f
--- /dev/null
+++ b/.pre-commit-config.yaml
@@ -0,0 +1,8 @@
+# See https://pre-commit.com for more information
+# See https://pre-commit.com/hooks.html for more hooks
+repos:
+-   repo: https://github.com/asottile/pyupgrade
+    rev: v2.20.0
+    hooks:
+    - id: pyupgrade
+      args: ['--keep-percent-format', '--py37-plus']
\ No newline at end of file
diff --git a/README.txt b/README.txt
index 4a4f34b..31eacce 100644
--- a/README.txt
+++ b/README.txt
@@ -179,3 +179,13 @@ You can put some configuration in ~/.config/eopayment.init ::
       order_id : 20201029093825_Vlco55
       test : True
       transaction_date : 2020-10-29 09:38:26+00:00
+
+Code Style
+==========
+
+pyupgrade is used to automatically upgrade syntax, using those parameters:
+
+    pyupgrade --keep-percent-format --py37-plus
+
+There is .pre-commit-config.yaml to use pre-commit to automatically pyupgrade
+before commits. (execute `pre-commit install` to install the git hook.)
diff --git a/tox.ini b/tox.ini
index ae874bb..ab7207f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,7 +4,7 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = py3
+envlist = py3,codestyle
 toxworkdir = {env:TMPDIR:/tmp}/tox-{env:USER}/eopayment/{env:BRANCH_NAME:}
 
 [testenv]
@@ -13,6 +13,7 @@ setenv =
   SETUPTOOLS_USE_DISTUTILS=stdlib
 commands =
   py3: py.test {posargs: --junitxml=junit-{envname}.xml --cov-report xml --cov-report html --cov=eopayment/ tests}
+  codestyle: pre-commit run --all-files --show-diff-on-failure
 usedevelop = True
 deps = coverage
   pytest
@@ -21,6 +22,7 @@ deps = coverage
   mock<4
   httmock
   lxml
+  pre-commit
 
 [pytest]
 filterwarnings =