Remove pytz from dependencies

Until now, icalendar was using pytz.
This removes the dependency pytz.
Tests run with pytz and without.
The CI also runs the tests without pytz.
The default implementation of icalendar uses zoneinfo.

.github/workflows/tests.yml

@@ -19,6 +19,7 @@ jobs:
         # [Python version, tox env]
         - ["3.7",   "py37"]
         - ["3.8",   "py38"]
+        - ["3.8",   "nopytz"]
         - ["3.9",   "py39"]
         - ["3.10",  "py310"]
         - ["pypy-3.9", "pypy3"]

setup.py

@@ -20,7 +20,6 @@ for fname in ['README.rst', 'CONTRIBUTING.rst', 'CHANGES.rst', 'LICENSE.rst']:
 tests_require = []
 install_requires = [
     'python-dateutil',
-    'pytz',
     # install requirements depending on python version
     # see https://www.python.org/dev/peps/pep-0508/#environment-markers
     'backports.zoneinfo; python_version == "3.7" or python_version == "3.8"',

src/icalendar/tests/conftest.py

@@ -4,7 +4,10 @@ except ImportError:
     import zoneinfo
 import pytest
 import icalendar
-import pytz
+try:
+    import pytz
+except ImportError:
+    pytz = None
 from datetime import datetime
 from dateutil import tz
 from icalendar.cal import Component, Calendar, Event, ComponentFactory
@@ -14,6 +17,21 @@ from pathlib import Path
 import itertools
 import sys
 
+HAS_PYTZ = pytz is not None
+if HAS_PYTZ:
+    PYTZ_UTC = [
+        pytz.utc,
+        pytz.timezone('UTC'),
+    ]
+    PYTZ_IN_TIMEZONE = [
+        lambda dt, tzname: pytz.timezone(tzname).localize(dt),
+    ]
+    PYTZ_TZP = ["pytz"]
+else:
+    PYTZ_UTC = []
+    PYTZ_IN_TIMEZONE = []
+    PYTZ_TZP = []
+
 
 class DataSource:
     '''A collection of parsed ICS elements (e.g calendars, timezones, events)'''
@@ -77,17 +95,14 @@ def timezones(tzp):
 def events(tzp):
     return DataSource(EVENTS_FOLDER, icalendar.Event.from_ical)
 
-@pytest.fixture(params=[
-    pytz.utc,
+@pytest.fixture(params=PYTZ_UTC + [
     zoneinfo.ZoneInfo('UTC'),
-    pytz.timezone('UTC'),
     tz.UTC,
     tz.gettz('UTC')])
 def utc(request, tzp):
     return request.param
 
-@pytest.fixture(params=[
-    lambda dt, tzname: pytz.timezone(tzname).localize(dt),
+@pytest.fixture(params=PYTZ_IN_TIMEZONE + [
     lambda dt, tzname: dt.replace(tzinfo=tz.gettz(tzname)),
     lambda dt, tzname: dt.replace(tzinfo=zoneinfo.ZoneInfo(tzname))
 ])
@@ -194,7 +209,7 @@ def tzp(tzp_name):
     _tzp.use_default()
 
 
-@pytest.fixture(params=["pytz", "zoneinfo"])
+@pytest.fixture(params=PYTZ_TZP + ["zoneinfo"])
 def other_tzp(request, tzp):
     """This is annother timezone provider.
 
@@ -229,12 +244,12 @@ def pytest_generate_tests(metafunc):
     See https://docs.pytest.org/en/6.2.x/example/parametrize.html#deferring-the-setup-of-parametrized-resources
     """
     if "tzp_name" in metafunc.fixturenames:
-        tzp_names = ["pytz", "zoneinfo"]
+        tzp_names = PYTZ_TZP + ["zoneinfo"]
         if "zoneinfo_only" in metafunc.fixturenames:
-            tzp_names.remove("pytz")
-        if "pytz_only" in  metafunc.fixturenames:
+            tzp_names = ["zoneinfo"]
+        if "pytz_only" in metafunc.fixturenames:
             tzp_names.remove("zoneinfo")
-        assert tzp_names, "Use pytz_only or zoneinfo_only but not both!"
+        assert not ("zoneinfo_only" in metafunc.fixturenames and "pytz_only" in metafunc.fixturenames), "Use pytz_only or zoneinfo_only but not both!"
         metafunc.parametrize("tzp_name", tzp_names, scope="module")
 
 
@@ -244,13 +259,19 @@ class DoctestZoneInfo(zoneinfo.ZoneInfo):
         return f"ZoneInfo(key={repr(self.key)})"
 
 
-def test_print(obj):
+def doctest_print(obj):
     """doctest print"""
     if isinstance(obj, bytes):
         obj = obj.decode("UTF-8")
     print(str(obj).strip().replace("\r\n", "\n").replace("\r", "\n"))
 
 
+def doctest_import(name, *args, **kw):
+    """Replace the import mechanism to skip the whole doctest if we import pytz."""
+    if name == "pytz":
+        return pytz
+    return __import__(name, *args, **kw)
+
 @pytest.fixture()
 def env_for_doctest(monkeypatch):
     """Modify the environment to make doctests run."""
@@ -258,4 +279,7 @@ def env_for_doctest(monkeypatch):
     monkeypatch.setattr(zoneinfo, "ZoneInfo", DoctestZoneInfo)
     from icalendar.timezone.zoneinfo import ZONEINFO
     monkeypatch.setattr(ZONEINFO, "utc", zoneinfo.ZoneInfo("UTC"))
-    return {"print": test_print}
+    return {
+        "print": doctest_print,
+        "__import__": doctest_import,
+    }

src/icalendar/tests/prop/test_identity_and_equality.py

@@ -2,7 +2,10 @@
 from icalendar import vDDDTypes
 from datetime import datetime, date, time
 from icalendar.timezone.zoneinfo import zoneinfo
-import pytz
+try:
+    import pytz
+except ImportError:
+    pytz = None
 from dateutil import tz
 import pytest
 from copy import deepcopy
@@ -10,7 +13,6 @@ from copy import deepcopy
 
 
 vDDDTypes_list = [
-    vDDDTypes(pytz.timezone('EST').localize(datetime(year=2022, month=7, day=22, hour=12, minute=7))),
     vDDDTypes(datetime(year=2022, month=7, day=22, hour=12, minute=7, tzinfo=zoneinfo.ZoneInfo("Europe/London"))),
     vDDDTypes(datetime(year=2022, month=7, day=22, hour=12, minute=7)),
     vDDDTypes(datetime(year=2022, month=7, day=22, hour=12, minute=7, tzinfo=tz.UTC)),
@@ -18,6 +20,8 @@ vDDDTypes_list = [
     vDDDTypes(date(year=2022, month=7, day=23)),
     vDDDTypes(time(hour=22, minute=7, second=2))
 ]
+if pytz:
+    vDDDTypes_list.append(vDDDTypes(pytz.timezone('EST').localize(datetime(year=2022, month=7, day=22, hour=12, minute=7))),)
 
 def identity(x):
     return x

src/icalendar/tests/test_equality.py

@@ -1,6 +1,9 @@
 """Test the equality and inequality of components."""
 import copy
-import pytz
+try:
+    import pytz
+except ImportError:
+    pytz = None
 from icalendar.prop import *
 from datetime import datetime, date, timedelta
 import pytest

src/icalendar/tests/test_pytz_zoneinfo_integration.py

@@ -2,19 +2,31 @@
 
 These are mostly located in icalendar.timezone.
 """
-import pytz
+try:
+    import pytz
+    from icalendar.timezone.pytz import PYTZ
+except ImportError:
+    pytz = None
 from icalendar.timezone.zoneinfo import zoneinfo, ZONEINFO
 from dateutil.tz.tz import _tzicalvtz
-from icalendar.timezone.pytz import PYTZ
 import pytest
 import copy
 import pickle
 from dateutil.rrule import rrule, MONTHLY
 from datetime import datetime
 
+if pytz:
+    PYTZ_TIMEZONES = pytz.all_timezones
+    TZP_ = [PYTZ(), ZONEINFO()]
+    NEW_TZP_NAME = ["pytz", "zoneinfo"]
+else:
+    PYTZ_TIMEZONES = []
+    TZP_ = [ZONEINFO()]
+    NEW_TZP_NAME = ["zoneinfo"]
 
-@pytest.mark.parametrize("tz_name", pytz.all_timezones + list(zoneinfo.available_timezones()))
-@pytest.mark.parametrize("tzp_", [PYTZ(), ZONEINFO()])
+
+@pytest.mark.parametrize("tz_name", PYTZ_TIMEZONES + list(zoneinfo.available_timezones()))
+@pytest.mark.parametrize("tzp_", TZP_)
 def test_timezone_names_are_known(tz_name, tzp_):
     """Make sure that all timezones are understood."""
     if tz_name in ("Factory", "localtime"):
@@ -55,7 +67,7 @@ def test_cache_reuse_timezone_cache(tzp, timezones):
     assert tzp1 is tzp.timezone("custom_Pacific/Fiji"), "Cache is not replaced."
 
 
-@pytest.mark.parametrize("new_tzp_name", ["pytz", "zoneinfo"])
+@pytest.mark.parametrize("new_tzp_name", NEW_TZP_NAME)
 def test_cache_is_emptied_when_tzp_is_switched(tzp, timezones, new_tzp_name):
     """Make sure we do not reuse the timezones created when we switch the provider."""
     tzp.cache_timezone_component(timezones.pacific_fiji)

src/icalendar/tests/test_with_doctest.py

@@ -14,6 +14,7 @@ import doctest
 import os
 import pytest
 import importlib
+import sys
 
 HERE = os.path.dirname(__file__) or "."
 ICALENDAR_PATH = os.path.dirname(HERE)
@@ -35,7 +36,12 @@ def test_this_module_is_among_them():
 @pytest.mark.parametrize("module_name", MODULE_NAMES)
 def test_docstring_of_python_file(module_name):
     """This test runs doctest on the Python module."""
-    module = importlib.import_module(module_name)
+    try:
+        module = importlib.import_module(module_name)
+    except ModuleNotFoundError as e:
+        if e.name == "pytz":
+            pytest.skip("pytz is not installed, skipping this module.")
+        raise
     test_result = doctest.testmod(module, name=module_name)
     assert test_result.failed == 0, f"{test_result.failed} errors in {module_name}"
 
@@ -68,11 +74,11 @@ def test_documentation_file(document, zoneinfo_only, env_for_doctest):
     functions are also replaced to work.
     """
     test_result = doctest.testfile(document, module_relative=False, globs=env_for_doctest)
+    if env_for_doctest.get("pytz") is None:
+        pytest.skip("pytz was imported but could not be used.")
     assert test_result.failed == 0, f"{test_result.failed} errors in {os.path.basename(document)}"
 
 
 def test_can_import_zoneinfo(env_for_doctest):
     """Allow importing zoneinfo for tests."""
-    import pytz
-    import zoneinfo
-    from dateutil import tz
+    assert "zoneinfo" in sys.modules

src/icalendar/timezone/tzp.py

@@ -8,7 +8,7 @@ from icalendar import prop
 from dateutil.rrule import rrule
 
 
-DEFAULT_TIMEZONE_PROVIDER = "pytz"
+DEFAULT_TIMEZONE_PROVIDER = "zoneinfo"
 
 
 class TZP:

tox.ini

@@ -1,6 +1,6 @@
 # to run for a specific environment, use ``tox -e ENVNAME``
 [tox]
-envlist = py37,py38,py39,py310,py311,pypy3,docs
+envlist = py37,py38,py39,py310,py311,pypy3,docs,nopytz
 # Note: the 'docs' env creates a 'build' directory which may interfere in strange ways
 # with the other environments.  You might see this when you run the tests in parallel.
 # See https://github.com/collective/icalendar/pull/359#issuecomment-1214150269
@@ -11,11 +11,30 @@ deps =
     pytest
     coverage
     hypothesis
+    pytz
 commands =
     coverage run --source=src/icalendar --omit=*/tests/hypothesis/* --omit=*/tests/fuzzed/* --module pytest []
     coverage report
     coverage html
 
+[testenv:nopytz]
+# install with dependencies
+usedevelop = False
+# use lowest version
+basepython = python3.8
+allowlist_externals =
+    rm
+deps =
+    setuptools>=70.1.0
+    pytest
+    coverage
+    hypothesis
+commands =
+    rm -rf build # do not mess up import
+    coverage run --source=src/icalendar --omit=*/tests/hypothesis/* --omit=*/tests/fuzzed/* --module pytest []
+    coverage report
+    coverage html
+
 [testenv:docs]
 deps =
     -r {toxinidir}/requirements_docs.txt