Why can't I display these dataframes?

[brady951]

I'm trying to take an average reading of radio scans I took at different locations. As I understand it I should have created a list of 5 dataframes. I can print them no problem. But I cannot plot them on a graph, nor can I apply a to_csv() function to them.

number_header_lines = 12
s=['40','50', '60', '70', '80']

for i in range(len(s)):  
    s1 = pd.read_csv(s[i]+'01.csv', header = number_header_lines, skipinitialspace = True)
    s2 = pd.read_csv(s[i]+'02.csv', header = number_header_lines, skipinitialspace = True)
    s3 = pd.read_csv(s[i]+'03.csv', header = number_header_lines, skipinitialspace = True)

    s_ave = (s1+s2+s3)/3
    print(s_ave)
    s_ave