BUG: Fix DataFrame.apply for string arg with additional args (#22376) (#22377)

Author: megabyde

doc/source/whatsnew/v0.24.0.txt

@@ -634,6 +634,7 @@ Numeric
   a ``TypeError`` was wrongly raised. For all three methods such calculation are now done correctly. (:issue:`16679`).
 - Bug in :class:`Series` comparison against datetime-like scalars and arrays (:issue:`22074`)
 - Bug in :class:`DataFrame` multiplication between boolean dtype and integer returning ``object`` dtype instead of integer dtype (:issue:`22047`,:issue:`22163`)
+- Bug in :meth:`DataFrame.apply` where, when supplied with a string argument and additional positional or keyword arguments (e.g. ``df.apply('sum', min_count=1)``), a ``TypeError`` was wrongly raised (:issue:`22376`)
 -
 
 Strings

pandas/core/apply.py

@@ -71,7 +71,9 @@ def __init__(self, obj, func, broadcast, raw, reduce, result_type,
         self.result_type = result_type
 
         # curry if needed
-        if kwds or args and not isinstance(func, np.ufunc):
+        if ((kwds or args) and
+                not isinstance(func, (np.ufunc, compat.string_types))):
+
             def f(x):
                 return func(x, *args, **kwds)
         else:

pandas/tests/frame/test_apply.py

@@ -120,14 +120,17 @@ def test_apply_standard_nonunique(self):
         rs = df.T.apply(lambda s: s[0], axis=0)
         assert_series_equal(rs, xp)
 
-    @pytest.mark.parametrize('arg', ['sum', 'mean', 'min', 'max', 'std'])
-    def test_with_string_args(self, arg):
-        result = self.frame.apply(arg)
-        expected = getattr(self.frame, arg)()
-        tm.assert_series_equal(result, expected)
-
-        result = self.frame.apply(arg, axis=1)
-        expected = getattr(self.frame, arg)(axis=1)
+    @pytest.mark.parametrize('func', ['sum', 'mean', 'min', 'max', 'std'])
+    @pytest.mark.parametrize('args,kwds', [
+        pytest.param([], {}, id='no_args_or_kwds'),
+        pytest.param([1], {}, id='axis_from_args'),
+        pytest.param([], {'axis': 1}, id='axis_from_kwds'),
+        pytest.param([], {'numeric_only': True}, id='optional_kwds'),
+        pytest.param([1, None], {'numeric_only': True}, id='args_and_kwds')
+    ])
+    def test_apply_with_string_funcs(self, func, args, kwds):
+        result = self.frame.apply(func, *args, **kwds)
+        expected = getattr(self.frame, func)(*args, **kwds)
         tm.assert_series_equal(result, expected)
 
     def test_apply_broadcast_deprecated(self):