TypeError: 'float' object is not iterable 3

The other answer is much more elegant than mine, but the following is closer to the spirit of your original code. It may make your errors more obvious. I apologize for the crappy formatting. I'm new to this site.

import csv
csvfile = open(r"C:\Users\Administrator\Downloads\canberra_2011_2012.csv")

header = csvfile.readline()  
csv_f = csv.reader(csvfile)
length = 0
total = 0.0   
for row in csv_f:
    first_value = float(row[5])
    total = total + first_value
    length += 1
if length > 0:
    average = total/length
    print("average = ",average)   

I think you want to collect all the first_values and then do some calculations. To do that, you must step through each row of the csv file and first collect all the values, otherwise you are summing one value and that's the source of your error.

Try this version:

import csv


with open(r"C:\Users\Administrator\Downloads\canberra_2011_2012.csv") as f:
    reader = csv.reader(f)
    values = [float(line[5]) for line in reader]

# Now you can do your calculations:

total = sum(values)
length = len(values)
# etc.

You are getting this error at this line of your code,

total = sum(first_value)

The error is raised because sum is a function of iterable object. As in your code, the first_value is a float object. So you can not use sum function on it. But when you use list compression,

first_value = [float(row[5]) for row in csv_f]

then the first_value is a list type object consisting the float values of row[5]. So you can apply sum function on it without raising error.

Apart from list compression, you can also append the values in a list in your for loop and calculate the sum and length after the loop.

first_values = []
for row in csv_f:
    first_value = float(row[5])
    first_values.append(first_value)

total = sum(first_values)
length = len(first_values)
average = total/length