dna | Python Fiddle

# user inputs the desired concentration
desired_concentration_in_ng_ul = float(input('Enter the desired concentration in ng/ul: '))

# user inputs the list of concentrations
concentrations_in_ng_ul = input('Enter the concentrations separated by a space: ')

# create a list from the input values
concentrations_list = [float(x) for x in concentrations_in_ng_ul.split()]

minimum_volume_ratio = 30

# output stuff
header_list = ['Sample', 'Initial Conc', 'Desired Conc', 'Dilution', 'Stock ul', 'dH20 ul']
master_output = []
master_output.append(header_list)

def calculate_concentrations(concentrations_list, master_output):
    for c in concentrations_list:

dilution_factor = c / desired_concentration_in_ng_ul

if dilution_factor < minimum_volume_ratio:
            stock_volume = minimum_volume_ratio / dilution_factor
            dilution_factor = minimum_volume_ratio
        else:
            stock_volume = 1

output_list = [' ', str(c), str(desired_concentration_in_ng_ul),
                       '{:03.2f}:{:03.2f}'.format(stock_volume, dilution_factor), '{:03.2f}'.format(stock_volume),
                       '{:03.2f}'.format(dilution_factor - stock_volume)]

master_output.append(output_list)

def output_results(master_output):

# determine column width by longest individual item
    col_width = max(len(word) for row in master_output for word in row) + 4  # padding

# print each column
    for row in master_output:
        print(''.join(word.ljust(col_width) for word in row))

calculate_concentrations(concentrations_list, master_output)
output_results(master_output)

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