DOC: align comment with PEP8 pandas-dev#41407

Author: t0asty

pandas/core/frame.py

@@ -8811,12 +8811,12 @@ def append(
 
         Examples
         --------
-        >>> df = pd.DataFrame([[1, 2], [3, 4]], columns=list('AB'), index=[0,2])
+        >>> df = pd.DataFrame([[1, 2], [3, 4]], columns=list('AB'), index=[0, 2])
         >>> df
            A  B
         0  1  2
         2  3  4
-        >>> df2 = pd.DataFrame([[5, 6], [7, 8]], columns=list('AB'), index=[0,2])
+        >>> df2 = pd.DataFrame([[5, 6], [7, 8]], columns=list('AB'), index=[0, 2])
         >>> df.append(df2)
            A  B
         0  1  2