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Defer SciPy and SymPy imports to cut `import spatialmath` time (~800 ms → ~150 ms)

Aperta
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Valutazione

Difficoltà
4/5
Tempo stimato
3-5 giorni
Idoneità per principianti
68/100
Tipo di issue
Refactoring
Chiarezza
Specificata chiaramente
Stato di attività
Attiva
Stack tecnologico
python
Ambito
performance, testing

Direzione di ricerca

Start by reading the top-level imports and mentioned methods in base/quaternions.py, spline.py, base/symbolic.py, and base/argcheck.py. Compare the import-time regression approach from #198, then verify that import spatialmath leaves neither scipy nor sympy in sys.modules while the affected feature and SymPy-supported paths still work.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

enhancement

Follow-up to #198, which deferred matplotlib.pyplot until something actually plots. Its description noted that scipy.interpolate and sympy cost about as much. They are now the main remaining costs of import spatialmath.

Where the time goes

Measured with python -X importtime -c "import spatialmath" on Python 3.12, macOS, Apple M1 (8 GB), warm cache. Cold-start times will be higher.

Module Cost Imported by
scipy.interpolate + scipy.spatial.transform ~455 ms base/quaternions.py:19, spline.py:14-15 (both at top level)
sympy (when installed) ~200 ms base/symbolic.py:19, via base/argcheck.py
matplotlib (no pyplot) ~100 ms geom2d.py:13 from matplotlib.path import Path. #198 kept this on purpose because Polygon2 needs it for its geometry
numpy ~40 ms
Total ~800 ms
SciPy: nothing needs it at import time
  • base/quaternions.py: the only user is qrand(). When the angle is limited, it does inverse-CDF sampling through _generate_inv_cdf_sin_squared_interp(), which is already @lru_cache'd. Every user pays ~440 ms for this one option. qslerp and the rest of the module don't use SciPy. Fix: move the import into that function, and make the -> interpolate.interp1d annotation a string or put it under TYPE_CHECKING.
  • spline.py: CubicSpline, RotationSpline, Rotation and BSpline are only used inside methods. Fix: import them inside those methods.
  • Both must change. If only one does, the other still loads scipy.interpolate. SciPy stays a hard dependency; only when it loads changes.
  • #129 (open) adds more top-level SciPy imports to spline.py (scipy.optimize, splrep) and would need the same treatment.
SymPy: avoid importing it just to check types

SymPy is optional. base/symbolic.py imports it inside a try so that issymbol() can check for sympy.Expr. But if "sympy" not in sys.modules, no argument can possibly be a SymPy expression. So issymbol() can return False without importing SymPy, and only import it once the user has imported SymPy themselves. This is a separate change from the SciPy one because argcheck is on almost every code path, so it needs its own testing (including the :SymPy: supported paths).

Expected result

About 150 ms for import spatialmath, and none of SciPy or SymPy loaded until a feature actually uses them. A regression test along the lines of #198's could assert that neither scipy nor sympy is in sys.modules after import spatialmath.

Lingua principale
Python
Stelle
643
Fork
102
Merge medio
11m
PR unite (30g)
1

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