styler.format options and validator tests

Author: attack68

pandas/core/config_init.py

@@ -793,6 +793,12 @@ def register_converter_cb(key):
     A formatter object to be used as default within ``Styler.format``.
 """
 
+
+def _is_formatter(x):
+    if not (x is None or callable(x) or isinstance(x, (dict, str))):
+        return ValueError("Value must have type 'callable, dict, str' or None.")
+
+
 with cf.config_prefix("styler"):
     cf.register_option("sparse.index", True, styler_sparse_index_doc, validator=bool)
 
@@ -838,5 +844,5 @@ def register_converter_cb(key):
         "format.formatter",
         None,
         styler_formatter,
-        validator=is_instance_factory([type(None), dict, callable, str]),
+        validator=_is_formatter,
     )

pandas/tests/io/formats/style/test_format.py

@@ -298,3 +298,15 @@ def test_format_options():
     with option_context("styler.format.formatter", {"int": "{:,.2f}"}):
         ctx_with_op = df.style._translate(True, True)
         assert ctx_with_op["body"][0][1]["display_value"] == "2,000.00"
+
+
+def test_format_options_validator():
+    df = DataFrame([[9]])
+    with option_context("styler.format.formatter", lambda x: f"{x:.3f}"):
+        assert " 9.000 " in df.style.to_latex()
+    with option_context("styler.format.formatter", "{:.2f}"):
+        assert " 9.00 " in df.style.to_latex()
+    with option_context("styler.format.formatter", {0: "{:.1f}"}):
+        assert " 9.0 " in df.style.to_latex()
+    with option_context("styler.format.formatter", None):
+        assert " 9 " in df.style.to_latex()