fix: lazy import scipy and matplotlib

Author: yaugenst-flex

tidy3d/components/medium.py

@@ -15,7 +15,6 @@
 import numpy as npo
 import pydantic.v1 as pd
 import xarray as xr
-from scipy import signal
 
 from tidy3d.components.material.tcad.heat import ThermalSpecType
 
@@ -3482,6 +3481,11 @@ def _real_partial_fraction_decomposition(
 
         """
 
+        try:
+            from scipy import signal
+        except ImportError:
+            raise ImportError("scipy is required to use this method.")
+
         if a.ndim != 1 or np.any(np.iscomplex(a)):
             raise ValidationError(
                 "Numerator coefficients must be a one-dimensional array of real numbers."

tidy3d/components/mode/mode_solver.py

@@ -11,8 +11,6 @@
 import numpy as np
 import pydantic.v1 as pydantic
 import xarray as xr
-from matplotlib.collections import PatchCollection
-from matplotlib.patches import Rectangle
 
 from ...constants import C_0
 from ...exceptions import SetupError, ValidationError
@@ -2315,6 +2313,13 @@ def _plot_pml(
         cls, simulation: Simulation, plane: Box, mode_spec: ModeSpec, ax: Ax = None
     ) -> Ax:
         """Plot the mode plane absorbing boundaries."""
+
+        try:
+            from matplotlib.collections import PatchCollection
+            from matplotlib.patches import Rectangle
+        except ImportError:
+            raise ImportError("matplotlib is required to plot the mode plane absorbing boundaries.")
+
         # Get the mode plane normal axis, center, and limits.
         _, h_lim, v_lim, _ = cls._center_and_lims(simulation=simulation, plane=plane)