make all pandas imports lazy

Author: SimonBlanke

src/gradient_free_optimizers/_memory.py

@@ -3,13 +3,16 @@
 # License: MIT License
 
 
+from __future__ import annotations
+
 import logging
 from multiprocessing.managers import DictProxy
-from typing import Any
-
-import pandas as pd
+from typing import TYPE_CHECKING, Any
 
 from ._objective_adapter import ObjectiveAdapter
+
+if TYPE_CHECKING:
+    import pandas as pd
 from ._storage import BaseStorage, MemoryStorage
 
 
@@ -39,6 +42,8 @@ def memory(self, warm_start: pd.DataFrame, memory: Any = None):
         if warm_start is None:
             return
 
+        import pandas as pd
+
         if not isinstance(warm_start, pd.DataFrame):
             logging.warning("Memory warm start must be of type pandas.DataFrame")
             logging.warning("Optimization will continue without memory warm start")

src/gradient_free_optimizers/_results_manager.py

@@ -2,9 +2,9 @@
 
 from typing import TYPE_CHECKING, Any
 
-import pandas as pd
-
 if TYPE_CHECKING:
+    import pandas as pd
+
     from .optimizers.core_optimizer.converter import Converter
 
 
@@ -45,11 +45,12 @@ def dataframe(self) -> pd.DataFrame:
         This reconstructs parameter dictionaries only when needed,
         avoiding the memory cost of storing them during optimization.
         """
+        import pandas as pd
+
         if not self._positions:
             return pd.DataFrame()
 
         if self._converter is None:
-            # Fallback: return just scores if no converter available
             return pd.DataFrame({"score": self._scores})
 
         # Build rows lazily

src/gradient_free_optimizers/ask_tell/direct_algorithm.py

@@ -3,9 +3,14 @@
 # License: MIT License
 """DIRECT algorithm optimizer with ask/tell interface."""
 
-import pandas as pd
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
 
 from .._ask_tell_mixin import AskTell
+
+if TYPE_CHECKING:
+    import pandas as pd
 from ..optimizers import DirectAlgorithm as _DirectAlgorithm
 
 

src/gradient_free_optimizers/optimizer_search/direct_algorithm.py

@@ -3,11 +3,14 @@
 # License: MIT License
 """DIRECT algorithm using adaptive hyperrectangle subdivision."""
 
-from typing import Literal
+from __future__ import annotations
 
-import pandas as pd
+from typing import TYPE_CHECKING, Literal
 
 from .._init_utils import get_default_initialize
+
+if TYPE_CHECKING:
+    import pandas as pd
 from ..optimizers import DirectAlgorithm as _DirectAlgorithm
 from ..search import Search