Source code for bokeh.util.dependencies

#-----------------------------------------------------------------------------
# Copyright (c) 2012 - 2020, Anaconda, Inc., and Bokeh Contributors.
# All rights reserved.
#
# The full license is in the file LICENSE.txt, distributed with this software.
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''' Utilities for checking dependencies

'''

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# Boilerplate
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import logging # isort:skip
log = logging.getLogger(__name__)

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# Imports
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# Standard library imports
from importlib import import_module
from types import ModuleType
from typing import Optional

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# Globals and constants
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__all__ = (
    'import_optional',
    'import_required',
)

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# General API
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def import_optional(mod_name: str) -> Optional[ModuleType]:
    ''' Attempt to import an optional dependency.

    Silently returns None if the requested module is not available.

    Args:
        mod_name (str) : name of the optional module to try to import

    Returns:
        imported module or None, if import fails

    '''
    try:
        return import_module(mod_name)
    except ImportError:
        pass
    except Exception:
        msg = "Failed to import optional module `{}`".format(mod_name)
        log.exception(msg)

    return None


def import_required(mod_name: str, error_msg: str) -> ModuleType:
    ''' Attempt to import a required dependency.

    Raises a RuntimeError if the requested module is not available.

    Args:
        mod_name (str) : name of the required module to try to import
        error_msg (str) : error message to raise when the module is missing

    Returns:
        imported module

    Raises:
        RuntimeError

    '''
    try:
        return import_module(mod_name)
    except ImportError as e:
        raise RuntimeError(error_msg) from e

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# Dev API
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# Private API
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# Code
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