Made all ``dateutil`` submodules lazily imported using `PEP 562

<https://www.python.org/dev/peps/pep-0562/>`_. On Python 3.7+, things like

``import dateutil; dateutil.tz.gettz("America/New_York")`` will now work

without explicitly importing ``dateutil.tz``, with the import occurring behind

the scenes on first use. The old behavior remains on Python 3.6 and earlier.

Fixed by Orson Adams. (gh issue #771, gh pr #1007)

import sys

def __getattr__(name):

import importlib

if name in __all__:

return importlib.import_module("." + name, __name__)

raise AttributeError(

"module {!r} has not attribute {!r}".format(__name__, name)

)

def __dir__():

# __dir__ should include all the lazy-importable modules as well.

return [x for x in globals() if x not in sys.modules] + __all__

import unittest

import six

MODULE_TYPE = type(sys)

if six.PY2:

filter_import_warning = pytest.mark.filterwarnings("ignore::RuntimeWarning")

else:

def filter_import_warning(f):

return f

def clean_import():

"""Create a somewhat clean import base for lazy import tests"""

du_modules = {

mod_name: mod

for mod_name, mod in sys.modules.items()

if mod_name.startswith("dateutil")

}

other_modules = {

mod_name for mod_name in sys.modules if mod_name not in du_modules

}

for mod_name in du_modules:

del sys.modules[mod_name]

yield

# Delete anything that wasn't in the origin sys.modules list

for mod_name in list(sys.modules):

if mod_name not in other_modules:

del sys.modules[mod_name]

# Restore original modules

for mod_name, mod in du_modules.items():

sys.modules[mod_name] = mod

def test_lazy_import(clean_import, module):

"""Test that dateutil.[submodule] works for py version > 3.7"""

import dateutil, importlib

if sys.version_info < (3, 7):

pytest.xfail("Lazy loading does not work for Python < 3.7")

mod_obj = getattr(dateutil, module, None)

assert isinstance(mod_obj, MODULE_TYPE)

mod_imported = importlib.import_module("dateutil.%s" % module)

assert mod_obj is mod_imported