


Combining Two DataFrames with Differing Indexes
You have a dataframe D and have extracted two dataframes A and B from it:
<code class="python">A = D[D.label == k] B = D[D.label != k]</code>
Your goal is to combine A and B into a single DataFrame, preserving the original order of data from D while retaining the indexes from D.
Solution via Deprecated Method
While DataFrame.append and Series.append are deprecated in v1.4.0, they can still be used for this task with the argument ignore_index set to True. This will discard the original indexes and reindex the combined dataframe from 0 to n-1.
<code class="python">df_merged = df1.append(df2, ignore_index=True)</code>
Solution with Preserved Indexes
If you want to retain the original indexes, set ignore_index to False. This will append the dataframes vertically and retain their respective indexes.
<code class="python">df_merged = df1.append(df2, ignore_index=False)</code>
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