Currency Translation in Python

I have a big dataframe consisting of U.S. Dollar statements and Canadian Dollar statements over a period of 20 years. I want to translate the Canadian statements to U.S.$ by dividing them with the average currency rates of that specific year. I can find the rows, but I cannot find the way to convert the numbers into U.S.$. Several column names are: Net profit, total assets, total liabilities and net foreign income. I use the following code to locate the rows in CAD $ for the year 1998:

firm[(firm['currency'] == 'CAD')&(firm['Year']== 1998)]