I am using this code to add a feature from GeoDatabase dataset to an open MXD file
<SPAN class="keyword token">import</SPAN> arcpy
mxd <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>MapDocument<SPAN class="punctuation token">(</SPAN>r<SPAN class="string token">"C:\Temp\Streets.mxd"</SPAN><SPAN class="punctuation token">)</SPAN>
df <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>ListDataFrames<SPAN class="punctuation token">(</SPAN>mxd<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"Layers"</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN>
targetGroupLayer <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>ListLayers<SPAN class="punctuation token">(</SPAN>mxd<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"Main"</SPAN><SPAN class="punctuation token">,</SPAN> df<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN>
addLayer <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>Layer<SPAN class="punctuation token">(</SPAN>r<SPAN class="string token">"C:\Data\NetMap.gdb\Streets\OneWay"</SPAN><SPAN class="punctuation token">)</SPAN>
arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>AddLayerToGroup<SPAN class="punctuation token">(</SPAN>df<SPAN class="punctuation token">,</SPAN> targetGroupLayer<SPAN class="punctuation token">,</SPAN> addLayer<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"BOTTOM"</SPAN><SPAN class="punctuation token">)</SPAN><SPAN
