习题15:名字格式化

格式化要求：
namelist([ {'name': 'Bart'}, {'name': 'Lisa'}, {'name': 'Maggie'} ])
# returns 'Bart, Lisa & Maggie'

namelist([ {'name': 'Bart'}, {'name': 'Lisa'} ])
# returns 'Bart & Lisa'

namelist([ {'name': 'Bart'} ])
# returns 'Bart'

namelist([])
# returns ''

def namelist(names):
    #your code here
    n = len(names)
    name_list = [e['name'] for e in names]
    if n < 2:
        return {
            0: '',
            1: '{}'
        }[n].format(*name_list)
    else:
        return ', '.join(name_list[:-1]) + ' & ' + name_list[-1]