"""

Stand-alone module to provide information about whether optional deps exist.

"""

from __future__ import absolute_import

import importlib

__all__ = ['get_module']

import_cache = {}

def get_module(name, raise_exc=False, msg=None):

"""

Return the module if it's available. Raise if desired.

A wrapper around importlib.import_module that only allows absolute import.

:param (str) name: Dot-separated module path. E.g., 'scipy.stats'.

:param (bool) raise_exc: Raise ImportError if not found?

:param (str|None) msg: Optional message to raise with ImportError.

:raises: (ImportError) If `raise_exception` is True, this can happen.

:return: (module|None) If import succeeds, the module will be returned.

"""

if name in import_cache:

return import_cache[name]

try:

module = importlib.import_module(name) # only allow absolute imports

except ImportError:

if raise_exc:

if msg is None:

raise # just raise the current import error

else:

raise ImportError(msg)

else:

import_cache[name] = module

return import_cache.get(name, None) # Don't store the None!