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import importlib
def relative_import(parent_name, rel_modules=(), rel_classes=()):
"""
Helper function to import submodules lazily in Python 3.7+
Parameters
----------
rel_modules: list of str
list of submodules to import, of the form .submodule
rel_classes: list of str
list of submodule classes/variables to import, of the form ._submodule.Foo
Returns
-------
tuple
Tuple that should be assigned to __all__, __getattr__ in the caller
"""
module_names = {rel_module.split(".")[-1]: rel_module for rel_module in rel_modules}
class_names = {rel_path.split(".")[-1]: rel_path for rel_path in rel_classes}
def __getattr__(import_name):
# In Python 3.7+, lazy import submodules
# Check for submodule
if import_name in module_names:
rel_import = module_names[import_name]
return importlib.import_module(rel_import, parent_name)
# Check for submodule class
if import_name in class_names:
rel_path_parts = class_names[import_name].split(".")
rel_module = ".".join(rel_path_parts[:-1])
class_name = import_name
class_module = importlib.import_module(rel_module, parent_name)
return getattr(class_module, class_name)
raise AttributeError(
"module {__name__!r} has no attribute {name!r}".format(
name=import_name, __name__=parent_name
)
)
__all__ = list(module_names) + list(class_names)
def __dir__():
return __all__
return __all__, __getattr__, __dir__
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