18.07.16 例题

例:

user_list = [{"name":"alex","hobby":"抽烟"},             {"name":"alex","hobby":"喝酒"},             {"name":"alex","hobby":"烫头"},             {"name":"wusir","hobby":"喊麦"},             {"name":"wusir","hobby":"街舞"}]==>[{‘name‘: ‘alex‘, ‘hobby_list‘: [‘抽烟‘, ‘喝酒‘, ‘烫头‘]},    {‘name‘: ‘wusir‘, ‘hobby_list‘: [‘喊麦‘, ‘街舞‘]}]

解题思路: 判断是否在result里面存在这个人的信息,如果不存在则新建一个字典,把hobby_list对应的value值放到一个列表中; 如果存在把hobby_list对应的列表加入一个hobby.

解题步骤:

user_list = [{"name":"alex","hobby":"抽烟"},             {"name":"alex","hobby":"喝酒"},             {"name":"alex","hobby":"烫头"},             {"name":"wusir","hobby":"喊麦"},             {"name":"wusir","hobby":"街舞"}]result = []for user in user_list:    for new_user in result:        if new_user["name"] == user["name"]:            new_user.setdefault("hobby_list",[]).append(user["hobby"])            break    else:        dic = {}        dic["name"] = user["name"]        dic["hobby_list"] = [user["hobby"]]        result.append(dic)print(result)

如果默认值参数是一个可变的数据类型,在调用的时候改变了.在其他位置看到的也跟着改变.

例:

def extendList(val, list=[]):    list.append(val)    return listlist1 = extendList(10)list2 = extendList(123, [])list3 = extendList(‘a‘)print(‘list1=%s‘ % list1)print(‘list2=%s‘ % list2)print(‘list3=%s‘ % list3)==>list1=[10, ‘a‘]   list2=[123]   list3=[10, ‘a‘]

原文地址：https://www.cnblogs.com/gxj742/p/9325418.html