make cyipopt/sudire optional dependency

- Default install: pip install direpack (without cyipopt/sudire)
- Full install: pip install direpack[ipopt] (includes cyipopt for sudire)
- sudire and ipopt_temp modules are conditionally imported

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: SvenSerneels

setup.py

@@ -77,8 +77,11 @@ def get_metadata():
         'scikit-learn>=0.18.0',
         'pandas>=0.19.0',
         'statsmodels>=0.8.0',
-        # 'ipopt>=0.1.5',
-        'dcor>=0.3'
-    ]
+        'dcor>=0.3',
+        'sympy>=1.0'
+    ],
+    extras_require={
+        'ipopt': ['cyipopt>=1.0.0'],
+    }
 )
 

src/direpack/__init__.py

@@ -12,8 +12,6 @@
 __version__ = "1.1.3"
 __date__ = "2024-05-23"
 
-# The commented lines can be uncommented if IPOPT has been installed independently.
-
 from .preprocessing.robcent import (
     VersatileScaler,
     versatile_scale,
@@ -32,9 +30,15 @@
 from .ppdire.ppdire import ppdire
 from .ppdire.capi import capi
 from .dicomo.dicomo import dicomo
-from .sudire.sudire import sudire, estimate_structural_dim
-from .plot.sudire_plot import sudire_plot
 from .plot.ppdire_plot import ppdire_plot
 from .plot.sprm_plot import sprm_plot, sprm_plot_cv
-from .ipopt_temp.ipopt_wrapper import minimize_ipopt
-from .ipopt_temp.jacobian import *
+
+# Optional imports requiring cyipopt (install with: pip install direpack[ipopt])
+try:
+    from .sudire.sudire import sudire, estimate_structural_dim
+    from .plot.sudire_plot import sudire_plot
+    from .ipopt_temp.ipopt_wrapper import minimize_ipopt
+    from .ipopt_temp.jacobian import *
+    IPOPT_AVAILABLE = True
+except ImportError:
+    IPOPT_AVAILABLE = False