Lazy import#

HyperSpy uses lazy imports to reduce the initial import time and memory footprint, as described in SPEC.

The following patterns are used in HyperSpy for lazy imports:

  • Libraries such as scipy, scikit-image are imported using, for example, import scipy instead of from scipy import ndimage to avoid loading submodules until they are needed.

  • Deferring expensive imports, such as dask, matplotlib or pint until they are needed inside functions or methods.

  • __getattr__ and __dir__ are used to implement lazy imports of HyperSpy objects, as described in PEP 562.

  • Lazily the import of signals and define lazy signals in separate modules from their non-signal counterparts to import dask only when needed, for example:

    In the module my_new_signal.py

    from hyperspy import signals

class MyNewSignal(signals.BaseSignal):
    # all of my great functions.

    In the module lazy_my_new_signal.py

    from hyperspy import signals
from my_package.my_new_signal import MyNewSignal

class LazyMyNewSignal(MyNewSignal, signals.LazySignal):
    """ Lazy signal for my new signal class"""

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