TYP: Add type hint for DataFrame.T and certain array types (#32532)

Author: qwhelan

pandas/core/arrays/categorical.py

@@ -1317,7 +1317,7 @@ def __setstate__(self, state):
  setattr(self, k, v)
 
  @property
- def T(self):
+ def T(self) -> "Categorical":
  """
  Return transposed numpy array.
  """

pandas/core/arrays/sparse/array.py

@@ -1296,14 +1296,14 @@ def mean(self, axis=0, *args, **kwargs):
  nsparse = self.sp_index.ngaps
  return (sp_sum + self.fill_value * nsparse) / (ct + nsparse)
 
- def transpose(self, *axes):
+ def transpose(self, *axes) -> "SparseArray":
  """
  Returns the SparseArray.
  """
  return self
 
  @property
- def T(self):
+ def T(self) -> "SparseArray":
  """
  Returns the SparseArray.
  """

pandas/core/frame.py

@@ -2445,7 +2445,9 @@ def transpose(self, *args, copy: bool = False) -> "DataFrame":
 
  return result.__finalize__(self)
 
- T = property(transpose)
+ @property
+ def T(self) -> "DataFrame":
+ return self.transpose()
 
  # ----------------------------------------------------------------------
  # Indexing Methods