Lets say I have a dataframe

```
df=pd.DataFrame({'Location': [ 'Ala', 'SS', 'Ala', 'Ala', 'SS', 'Ala', 'SS', 'TXE', 'TXE', 'TXE'],
                 'Bid': ['E','N','E','N','N','E', 'E',np.nan,np.nan,'A']})

```

Where S is sealed bids, N is people who did not bid, Nan is not present, and O is open bid.

I want to do a calculate the percentage of bidders where the equation would be (E+A)/(E+A+N). Is the best way to do a pivot table then implement the equation?

```
df=pd.DataFrame({'Location': [ 'Ala', 'SS', 'Ala', 'Ala', 'SS', 'Ala', 'SS', 'TXE', 'TXE', 'TXE'],
                 'Bid': ['E','N','E','N','N','E', 'E',np.nan,np.nan,'A']})

pt = df.pivot_table(rows='Location', cols='Bid', aggfunc='size', fill_value=0)

pt['Percentage']=(pt.A + pt.E)/(pt.A+pt.E+pt.N)
print (pt)

>>> 
Bid       A  E  N  Percentage
Location                     
Ala       0  3  1    0.750000
SS        0  1  2    0.333333
TXE       1  0  0    1.000000

[3 rows x 4 columns]

```

Is this the best way to calculate percentage or is there a better way than pivot tables?