I'm going to assume that this table is within ArcMap because you calculated the area of each feature in the third column. To extract values from a table that resides in a current ArcMap document, you need to use cursors. These ArcPython objects loop through each row in a table and allow you read and/or write to that table. If you are only reading information, the loop will be much faster if you use a SearchCursor; if you want to edit table values, you'll have to use an UpdateCursor.
There are a lot of different ways to go with cursors, but the simplest thing to sum the total area of all features, store it in a variable, then run the division for each feature and store the % of the total in a new field called "Percent_Area" or something like that. I'm assuming you know basic Python.
import arcpy
#Below is the name of the table layer in ArcMap.
InputTable = "My Table"
#This searchCursor reads the total area of all features.
TotalArea = 0.0
TableCursor = arcpy.SearchCursor(InputTable)
for TableRow in TableCursor:
TotalArea += TableRow.getValue("F_AREA")
del TableRow
del TableCursor
#At this point 'TotalArea' variable is the sum of all feature areas
#This updateCursor saves the % values for each feature
arcpy.AddField_management(InputTable,"Percent_Area","DOUBLE")
TableCursor = arcpy.UpdateCursor(InputTable)
for TableRow in TableCursor:
CurrentArea = TableRow.getValue("F_AREA")
# area for this feature
TableRow.setValue("Percent_Area",CurrentArea/TotalArea*100.0)
# relative area percentage for this feature
TableCursor.updateRow(TableRow)
del TableRow
del TableCursor
For such a small table and such a simple operation it would probably be easiest to just run Summary Statistics to get the total area and then do Field Calculator on a new field to calculate the percentage, but I'm assuming you are using Python for a reason.
