BUG: Fix NDFrame.interpolate non-existent variable pandas-dev#29132

NDFrame.interpolate fails if axis is specified by name and not integer

Author: ellequelle

doc/source/whatsnew/v1.0.0.rst

@@ -249,6 +249,7 @@ Bug fixes
 ~~~~~~~~~
 
 - Bug in :meth:`DataFrame.to_html` when using ``formatters=<list>`` and ``max_cols`` together. (:issue:`25955`)
+- Bug in :func:`pandas.core.generic.NDFrame.interpolate` where specifying axis by name references variable before it is assigned (:issue:`29132`)
 
 Categorical
 ^^^^^^^^^^^

pandas/core/generic.py

@@ -7023,13 +7023,16 @@ def interpolate(
         """
         inplace = validate_bool_kwarg(inplace, "inplace")
 
+        axis = self._get_axis_number(axis)
+
         if axis == 0:
             ax = self._info_axis_name
             _maybe_transposed_self = self
         elif axis == 1:
             _maybe_transposed_self = self.T
             ax = 1
         else:
+            ax = axis
             _maybe_transposed_self = self
         ax = _maybe_transposed_self._get_axis_number(ax)