Simpler way to specify conditional dependency

setup.py

@@ -2,7 +2,6 @@
 # -*- coding: utf-8 -*-
 
 from setuptools import setup
-import sys
 
 ver_dic = {}
 version_file = open("pytools/version.py")
@@ -13,17 +12,6 @@ finally:
 
 exec(compile(version_file_contents, "pytools/version.py", "exec"), ver_dic)
 
-version = sys.version_info
-requirements = [
-          "decorator>=3.2.0",
-          "appdirs>=1.4.0",
-          "six>=1.8.0",
-          "numpy>=1.6.0",
-          ]
-
-if version[0] == 3 and version[1] == 6:
-    requirements.append("dataclasses>=0.7")
-
 setup(name="pytools",
       version=ver_dic["VERSION_TEXT"],
       description="A collection of tools for Python",
@@ -49,7 +37,13 @@ setup(name="pytools",
 
       python_requires="~=3.6",
 
-      install_requires=requirements,
+      install_requires=[
+          "decorator>=3.2.0",
+          "appdirs>=1.4.0",
+          "six>=1.8.0",
+          "numpy>=1.6.0",
+          "dataclasses>=0.7;python_version<='3.6'"
+          ],
 
       package_data={"pytools": ["py.typed"]},