There are many methods to do it but personally I'll suggest you to use mask, for instance check this example:
from pandas import DataFrame
# Create data set
q = {'Revenue':[200,112,221],
'Cost':[331,441,551]}
df = DataFrame(q)
# mask = Return True when the value in column "Revenue" is equal to 111
mask = df['Revenue'] == 112
print mask
# Result:
# 0 False
# 1 True
# 2 False
# Name: Revenue, dtype: bool
# Select * FROM df WHERE Revenue = 112
df[mask]
# Result:
# Cost Revenue
# 1 441 112
