importers.py

importimportlib


defrelative_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_moduleforrel_moduleinrel_modules}
class_names= {rel_path.split(".")[-1]: rel_pathforrel_pathinrel_classes}

def__getattr__(import_name):
# In Python 3.7+, lazy import submodules

# Check for submodule
ifimport_nameinmodule_names:
rel_import=module_names[import_name]
returnimportlib.import_module(rel_import, parent_name)

# Check for submodule class
ifimport_nameinclass_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)
returngetattr(class_module, class_name)

raiseAttributeError(
"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__