Add ability to use float-tuple like kwarg legend(loc...) for rcParams['legend.loc'] matplotlib#22338

Author: NoyHanan

doc/users/next_whats_new/rcParams[legend.loc]_supports_float_tuple.rst

@@ -0,0 +1,5 @@
+``rcParams['legend.loc']`` now accepts float-tuple inputs
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The :rc:`legend.loc` rcParams now accepts float-tuple inputs, same as the *loc* keyword argument to `.Legend`.
+This allows users to set the location of the legend in a more flexible and consistent way.

lib/matplotlib/rcsetup.py

@@ -718,6 +718,51 @@ def visit_Attribute(self, node):
         self.generic_visit(node)
 
 
+# A validator dedicated to the named legend loc
+_validate_named_legend_loc = ValidateInStrings(
+    'legend.loc',
+    [
+        "best",
+        "upper right", "upper left", "lower left", "lower right", "right",
+        "center left", "center right", "lower center", "upper center",
+        "center"],
+    ignorecase=True)
+
+
+def _validate_legend_loc(loc):
+    """
+    Confirm that loc is a type which rc.Params["legend.loc"] supports.
+
+    .. versionadded:: 3.8
+
+    Parameters
+    ----------
+    loc : str | int | (float, float) | str((float, float))
+        The location of the legend.
+
+    Returns
+    -------
+    loc : str | int | (float, float) or raise ValueError exception
+        The location of the legend.
+    """
+    if isinstance(loc, str):
+        try:
+            return _validate_named_legend_loc(loc)
+        except ValueError:
+            pass
+        try:
+            loc = ast.literal_eval(loc)
+        except (SyntaxError, ValueError):
+            pass
+    if isinstance(loc, int):
+        if 0 <= loc <= 10:
+            return loc
+    if isinstance(loc, tuple):
+        if len(loc) == 2 and all(isinstance(e, Real) for e in loc):
+            return loc
+    raise ValueError(f"{loc} is not a valid legend location.")
+
+
 def validate_cycler(s):
     """Return a Cycler object from a string repr or the object itself."""
     if isinstance(s, str):
@@ -1042,11 +1087,7 @@ def _convert_validator_spec(key, conv):
 
     # legend properties
     "legend.fancybox": validate_bool,
-    "legend.loc": _ignorecase([
-        "best",
-        "upper right", "upper left", "lower left", "lower right", "right",
-        "center left", "center right", "lower center", "upper center",
-        "center"]),
+    "legend.loc": _validate_legend_loc,
 
     # the number of points in the legend line
     "legend.numpoints":      validate_int,

lib/matplotlib/tests/test_rcparams.py

@@ -1,7 +1,6 @@
 import copy
 import os
 from pathlib import Path
-import re
 import subprocess
 import sys
 from unittest import mock
@@ -592,8 +591,33 @@ def test_deprecation(monkeypatch):
     # suppress_matplotlib_deprecation_warning, rather than any explicit check.
 
 
-def test_rcparams_legend_loc():
-    value = (0.9, .7)
-    match_str = f"{value} is not a valid value for legend.loc;"
-    with pytest.raises(ValueError, match=re.escape(match_str)):
-        mpl.RcParams({'legend.loc': value})
+@pytest.mark.parametrize("value", [
+    "best",
+    1,
+    "1",
+    (0.9, .7),
+    (-0.9, .7),
+    "(0.9, .7)"
+])
+def test_rcparams_legend_loc(value):
+    # rcParams['legend.loc'] should allow any of the following formats.
+    # if any of these are not allowed, an exception will be raised
+    # test for gh issue #22338
+    mpl.rcParams["legend.loc"] = value
+
+
+@pytest.mark.parametrize("value", [
+    "best",
+    1,
+    (0.9, .7),
+    (-0.9, .7),
+])
+def test_rcparams_legend_loc_from_file(tmpdir, value):
+    # rcParams['legend.loc'] should be settable from matplotlibrc.
+    # if any of these are not allowed, an exception will be raised.
+    # test for gh issue #22338
+    rc_path = tmpdir.join("matplotlibrc")
+    rc_path.write(f"legend.loc: {value}")
+
+    with mpl.rc_context(fname=rc_path):
+        assert mpl.rcParams["legend.loc"] == value