PERF: load plotting entrypoint only when necessary

asv_bench/benchmarks/plotting.py

@@ -1,5 +1,9 @@
+import importlib
+import sys
+
 import matplotlib
 import numpy as np
+import pkg_resources
 
 from pandas import (
     DataFrame,
@@ -13,6 +17,8 @@
 except ImportError:
     from pandas.tools.plotting import andrews_curves
 
+from pandas.plotting._core import _get_plot_backend
+
 matplotlib.use("Agg")
 
 
@@ -99,4 +105,28 @@ def time_plot_andrews_curves(self):
         andrews_curves(self.df, "Name")
 
 
+class BackendLoading:
+    repeat = 1
+    number = 1
+    warmup_time = 0
+
+    def setup(self):
+        dist = pkg_resources.get_distribution("pandas")
+        spec = importlib.machinery.ModuleSpec("my_backend", None)
+        mod = importlib.util.module_from_spec(spec)
+        mod.plot = lambda *args, **kwargs: 1
+
+        backends = pkg_resources.get_entry_map("pandas")
+        my_entrypoint = pkg_resources.EntryPoint(
+            "pandas_plotting_backend", mod.__name__, dist=dist
+        )
+        backends["pandas_plotting_backends"][mod.__name__] = my_entrypoint
+        for i in range(10):
+            backends["pandas_plotting_backends"][str(i)] = my_entrypoint
+        sys.modules["my_backend"] = mod
+
+    def time_get_plot_backend(self):
+        _get_plot_backend("my_backend")
+
+
 from .pandas_vb_common import setup  # noqa: F401 isort:skip

doc/source/whatsnew/v1.3.0.rst

@@ -812,6 +812,7 @@ Performance improvements
 - Performance improvement in :meth:`.GroupBy.cummin` and :meth:`.GroupBy.cummax` with nullable data types (:issue:`37493`)
 - Performance improvement in :meth:`Series.nunique` with nan values (:issue:`40865`)
 - Performance improvement in :meth:`DataFrame.transpose`, :meth:`Series.unstack` with ``DatetimeTZDtype`` (:issue:`40149`)
+- Performance improvement in :meth:`Series.plot` and :meth:`DataFrame.plot` with entry point lazy loading (:issue:`41492`)
 
 .. ---------------------------------------------------------------------------
 

pandas/plotting/_core.py

@@ -1,11 +1,14 @@
 from __future__ import annotations
 
 import importlib
+import types
 from typing import (
     TYPE_CHECKING,
     Sequence,
 )
 
+import pkg_resources
+
 from pandas._config import get_option
 
 from pandas._typing import IndexLabel
@@ -865,7 +868,7 @@ def _get_call_args(backend_name, data, args, kwargs):
         if args and isinstance(data, ABCSeries):
             positional_args = str(args)[1:-1]
             keyword_args = ", ".join(
-                f"{name}={repr(value)}" for (name, default), value in zip(arg_def, args)
+                f"{name}={repr(value)}" for (name, _), value in zip(arg_def, args)
             )
             msg = (
                 "`Series.plot()` should not be called with positional "
@@ -876,7 +879,7 @@ def _get_call_args(backend_name, data, args, kwargs):
             )
             raise TypeError(msg)
 
-        pos_args = {name: value for value, (name, _) in zip(args, arg_def)}
+        pos_args = {name: value for (name, _), value in zip(arg_def, args)}
         if backend_name == "pandas.plotting._matplotlib":
             kwargs = dict(arg_def, **pos_args, **kwargs)
         else:
@@ -1724,91 +1727,90 @@ def hexbin(self, x, y, C=None, reduce_C_function=None, gridsize=None, **kwargs):
         return self(kind="hexbin", x=x, y=y, C=C, **kwargs)
 
 
-_backends = {}
+_backends: dict[str, types.ModuleType] = {}
 
 
-def _find_backend(backend: str):
+def _load_backend(backend: str) -> types.ModuleType:
     """
-    Find a pandas plotting backend>
+    Load a pandas plotting backend.
 
     Parameters
     ----------
     backend : str
         The identifier for the backend. Either an entrypoint item registered
-        with pkg_resources, or a module name.
-
-    Notes
-    -----
-    Modifies _backends with imported backends as a side effect.
+        with pkg_resources, "matplotlib", or a module name.
 
     Returns
     -------
     types.ModuleType
         The imported backend.
     """
-    import pkg_resources  # Delay import for performance.
+    if backend == "matplotlib":
+        # Because matplotlib is an optional dependency and first-party backend,
+        # we need to attempt an import here to raise an ImportError if needed.
+        try:
+            module = importlib.import_module("pandas.plotting._matplotlib")
+        except ImportError:
+            raise ImportError(
+                "matplotlib is required for plotting when the "
+                'default backend "matplotlib" is selected.'
+            ) from None
+        return module
+
+    found_backend = False
 
     for entry_point in pkg_resources.iter_entry_points("pandas_plotting_backends"):
-        if entry_point.name == "matplotlib":
-            # matplotlib is an optional dependency. When
-            # missing, this would raise.
-            continue
-        _backends[entry_point.name] = entry_point.load()
+        found_backend = entry_point.name == backend
+        if found_backend:
+            module = entry_point.load()
+            break
 
-    try:
-        return _backends[backend]
-    except KeyError:
+    if not found_backend:
         # Fall back to unregistered, module name approach.
         try:
             module = importlib.import_module(backend)
+            found_backend = True
         except ImportError:
             # We re-raise later on.
             pass
-        else:
-            if hasattr(module, "plot"):
-                # Validate that the interface is implemented when the option
-                # is set, rather than at plot time.
-                _backends[backend] = module
-                return module
+
+    if found_backend:
+        if hasattr(module, "plot"):
+            # Validate that the interface is implemented when the option is set,
+            # rather than at plot time.
+            return module
 
     raise ValueError(
-        f"Could not find plotting backend '{backend}'. Ensure that you've installed "
-        f"the package providing the '{backend}' entrypoint, or that the package has a "
-        "top-level `.plot` method."
+        f"Could not find plotting backend '{backend}'. Ensure that you've "
+        f"installed the package providing the '{backend}' entrypoint, or that "
+        "the package has a top-level `.plot` method."
     )
 
 
-def _get_plot_backend(backend=None):
+def _get_plot_backend(backend: str | None = None):
     """
     Return the plotting backend to use (e.g. `pandas.plotting._matplotlib`).
 
-    The plotting system of pandas has been using matplotlib, but the idea here
-    is that it can also work with other third-party backends. In the future,
-    this function will return the backend from a pandas option, and all the
-    rest of the code in this file will use the backend specified there for the
-    plotting.
+    The plotting system of pandas uses matplotlib by default, but the idea here
+    is that it can also work with other third-party backends. This function
+    returns the module which provides a top-level `.plot` method that will
+    actually do the plotting. The backend is specified from a string, which
+    either comes from the keyword argument `backend`, or, if not specified, from
+    the option `pandas.options.plotting.backend`. All the rest of the code in
+    this file uses the backend specified there for the plotting.
 
     The backend is imported lazily, as matplotlib is a soft dependency, and
     pandas can be used without it being installed.
+
+    Notes
+    -----
+    Modifies `_backends` with imported backend as a side effect.
     """
     backend = backend or get_option("plotting.backend")
 
-    if backend == "matplotlib":
-        # Because matplotlib is an optional dependency and first-party backend,
-        # we need to attempt an import here to raise an ImportError if needed.
-        try:
-            import pandas.plotting._matplotlib as module
-        except ImportError:
-            raise ImportError(
-                "matplotlib is required for plotting when the "
-                'default backend "matplotlib" is selected.'
-            ) from None
-
-        _backends["matplotlib"] = module
-
     if backend in _backends:
         return _backends[backend]
 
-    module = _find_backend(backend)
+    module = _load_backend(backend)
     _backends[backend] = module
     return module