mutable and immutable

employees = ['Corey', 'John', 'Rick', 'Steve', 'Carl', 'Adam']

output = '<ul>\n'

for employee in employees:
    output += '\t<li>{}>/li>\n'.format(employee)
    print ('Address of output is {}'.format(id(output)))

output += '</ul>'

print (output)

print ('\n')

Address of output is 140124326580488
Address of output is 140124326539664
Address of output is 140124327332232
Address of output is 140124326588704
Address of output is 140124327673344
Address of output is 140124327114728
<ul>
	<li>Corey>/li>
	<li>John>/li>
	<li>Rick>/li>
	<li>Steve>/li>
	<li>Carl>/li>
	<li>Adam>/li>
</ul>