如何调试此错误？ 'generator'类型的对象没有len（）

Question

I'm trying to compute the mean values of the numbers in a list of lists, I'm supposed to skip over the first observation (ie position 0) because they are the names of countries, I only need to calculate the mean of every column after [0] . However, my code keeps saying:

TypeError: object of type 'generator' has no len()

If anyone could have a look and offer some help, I would greatly appreciate it. Thank you!

I've tried this code:

def my_mean1(file):    
    mean_list = []
    for column in range(1,len(file[0])):
        column_values = (row[column] for row in file)

        # calculate the mean but not with the statistics module
        mean_values = sum(column_values) / len(column_values)
        mean_list.append(mean_values(x for x in column_values if x is not None))    
    return mean_list

The results I expect

test = [['str1', 2.66171813, 7.460143566, 0.490880072, 52.33952713, 0.427010864, -0.106340349, 0.261178523], ['str2', 4.639548302, 9.373718262, 0.637698293, 69.05165863, 0.74961102, -0.035140377, 0.457737535]]

test1 = data(file) # a function that made the list of lists

my_mean(test)
[5.022380471333333, 9.327360550833333, 0.7483190200000001, 65.42301750166666, 0.6615842928333333, -0.05882061216666667, 0.3449308604]

but the error I encounter when I use test

TypeError: object of type 'generator' has no len()

and the error I encounter when I try test1

TypeError: unsupported operand type(s) for +: 'int' and 'str'

Answer 1

column_values = (row[column] for row in file)

Replace the parenthesis with square brackets so you get a list returned instead of the generator type. []