Solutions

`

def read_csv_to_floats(filename):
    '''
    Take string parameters as csv filename
    Read in and process file, converting all elements to floats.

    Return as 2D list (list of lists)
    '''

    with open(filename) as file:
        data_string = file.readlines()
    data_floats = []
    for line in data_string:
        tmp_floats = []
        tmp_list = line.split(',')
        for item in tmp_list:
            tmp_floats.append( float(item) )
        data_floats.append(tmp_floats)
    return data_floats

Arithmetic on the Command Line

import sys


def do_arithmetic(operand1, operator, operand2):

    if operator == 'add':
        value = operand1 + operand2
    elif operator == 'subtract':
        value = operand1 - operand2
    elif operator == 'multiply':
        value = operand1 * operand2
    elif operator == 'divide':
        value = operand1 / operand2
    print(value)

def main():
    assert len(sys.argv) == 4, 'Need exactly 3 arguments'

    operator = sys.argv[1]
    assert operator in ['add', 'subtract', 'multiply', 'divide'], \
        'Operator is not one of add, subtract, multiply, or divide: bailing out'
    try:
        operand1, operand2 = float(sys.argv[2]), float(sys.argv[3])
    except ValueError:
        print('cannot convert input to a number: bailing out')
        return

    do_arithmetic(operand1, operator, operand2)

if __name__ == '__main__':
   main()

Check that your solution works by trying the different componenets and a few different values.

Couting Lines

#!/usr/bin/env python3
import sys

def main():
    '''print each input filename and the number of lines in it,
       and print the sum of the number of lines'''
    filenames = sys.argv[1:]
    sum_nlines = 0 #initialize counting variable

    if len(filenames) == 0: # no filenames, advise usage
        print("Please provide filenames in order to count number of lines")
    else:
        for f in filenames:
            n = count_file(f)
            print('%s %d' % (f, n))
            sum_nlines += n
        print('total: %d' % sum_nlines)

def count_file(filename):
    '''count the number of lines in a file'''
    f = open(filename,'r')
    nlines = len(f.readlines())
    f.close()
    return(nlines)

if __name__ == '__main__':
   main()

If you have used inflammatio_mean.py as the basis for this program then you will have a very different solution.