Using python to find the most common value(s) in the column of CSV file

for each in column_names:
    print each + ':'
    for L in range(1,len(row_list)):
        each_column = columns[each][L]
        for i in each_column:
            if i == i.index(i)+1:
                count+=1
                mode=i

The above is my attempt to find the most common values in the column of a .csv file. The code is incomplete and I'm stack for hours to get this right.

I'm very new to python, even the syntaxes is unfamiliar to me. All help will definitely be appreciated.