calculate percentage row by row in pandas dataframe

Question

I have a dataframe, df, i want to calculate percentage by row for one of the rows and return 'No' in the other row.

A	B	C	D
X	500	250	50.00
Y	980	700	71.42

A	B	C	D	E
X	500	250	50.00	70.08
Y	980	700	71.42	No

70.08% is got by dividing 50.00/71.42

Answer 1

# shift by a row and divide the two values

df['E']=df['D'].div(df['D'].shift(-1)).fillna('No')
df

    A     B       C         D   E
0   X   500     250     50.00   0.700084
1   Y   980     700     71.42   No