Python3在列表中的字典中查找值

Question

我创建了一个 function，我在其中将人员及其可用性添加到名为游戏玩家的列表中。 我希望 function 有两个例外。 如果此人忘记添加他们的姓名或他们的可用性，我将打印：“玩家缺少关键信息”

如果名称已经在列表中，我也希望出现错误并打印：“此名称已存在”

但是我似乎找不到在列表中获取值字典 [“name”] 的方法。

我也试过 gamers[0]["name"] 但这没有用。

gamers = []

def add_gamer(gamer, gamers):
    if gamer.get("name") and gamer.get("availability"):
        gamers.append(gamer)
    elif gamers["name"] in gamers:                      #Here is the problem
        print("This name already exists")
    else:
        print("Gamer missing critical information")
    return gamers

kimberly = {
    'name': "Kimberly Warner",
    'availability': ["Monday", "Tuesday", "Friday"]
}
print(add_gamer(kimberly, gamers))

add_gamer({'name':'Thomas Nelson','availability': ["Tuesday", "Thursday", "Saturday"]}, gamers)
add_gamer({'name':'Joyce Sellers','availability': ["Monday", "Wednesday", "Friday", "Saturday"]}, gamers)
add_gamer({'name':'Michelle Reyes','availability': ["Wednesday", "Thursday", "Sunday"]}, gamers)
add_gamer({'name':'Stephen Adams','availability': ["Thursday", "Saturday"]}, gamers)
add_gamer({'name': 'Joanne Lynn', 'availability': ["Monday", "Thursday"]}, gamers)
add_gamer({'name':'Latasha Bryan','availability': ["Monday", "Sunday"]}, gamers)
add_gamer({'name':'Crystal Brewer','availability': ["Thursday", "Friday", "Saturday"]}, gamers)
add_gamer({'name':'James Barnes Jr.','availability': ["Tuesday", "Wednesday", "Thursday", "Sunday"]}, gamers)
add_gamer({'name':'Michel Trujillo','availability': ["Monday", "Tuesday", "Wednesday"]}, gamers)


add_gamer({'name':'Thomas Nelson','availability': ["Tuesday", "Thursday", "Saturday"]}, gamers)
print(gamers)

#this last line (which ads Thomas Nelson) should return: "This name is already in the list"

Answer 1

尝试切换顺序并检查：

if any(g['name'] == gamer["name"] for g in gamers):
    print("This name already exists")
elif gamer.get("name") and gamer.get("availability"):
    gamers.append(gamer)
    

Answer 2

在您的代码中，您首先附加元素，然后检查它是否存在。 所以， efif 部分基本上什么都不做。 所以，改变它的顺序。

gamers = []

def add_gamer(gamer, gamers):
    for gam in gamers:
        if gam['name'] == gamer['name']:#Here is the problem
            print("This name already exists")
            return gamers
    if gamer.get("name") and gamer.get("availability"):
        gamers.append(gamer)
    else:
        print("Gamer missing critical information")
    return gamers

kimberly = {
    'name': "Kimberly Warner",
    'availability': ["Monday", "Tuesday", "Friday"]
}
print(add_gamer(kimberly, gamers))

add_gamer({'name':'Thomas Nelson','availability': ["Tuesday", "Thursday", "Saturday"]}, gamers)
add_gamer({'name':'Joyce Sellers','availability': ["Monday", "Wednesday", "Friday", "Saturday"]}, gamers)
add_gamer({'name':'Michelle Reyes','availability': ["Wednesday", "Thursday", "Sunday"]}, gamers)
add_gamer({'name':'Stephen Adams','availability': ["Thursday", "Saturday"]}, gamers)
add_gamer({'name': 'Joanne Lynn', 'availability': ["Monday", "Thursday"]}, gamers)
add_gamer({'name':'Latasha Bryan','availability': ["Monday", "Sunday"]}, gamers)
add_gamer({'name':'Crystal Brewer','availability': ["Thursday", "Friday", "Saturday"]}, gamers)
add_gamer({'name':'James Barnes Jr.','availability': ["Tuesday", "Wednesday", "Thursday", "Sunday"]}, gamers)
add_gamer({'name':'Michel Trujillo','availability': ["Monday", "Tuesday", "Wednesday"]}, gamers)


add_gamer({'name':'Thomas Nelson','availability': ["Tuesday", "Thursday", "Saturday"]}, gamers)
print(gamers)

#this last line (which ads Thomas Nelson) should return: "This name is already in the list"

Answer 3

• 你的elif条件永远不会命中。 （这就是您没有收到错误的原因，否则列表的gamers["name"]会给出错误。
• 即使您更正了if顺序，即使您将其设为 gamer['name']，您也会在list中插入一个dict ，然后检查str是否在列表中。

您可以定义 function 以通过给定的键值对在 dict 列表中搜索。

def search_list_of_dict(_list, _key, _value):
    return [el for el in _list if el.get(_key) == _value]

所以你的 function 定义变成了，

gamers = []

def add_gamer(gamer, gamers):
    if gamer.get("name") and gamer.get("availability"):
        if search_list_of_list(gamers, 'name', gamer.get("name"):
            print("This name already exists")
            return False
        else:
            gamers.append(gamer)
            return True
    else:
        print("Gamer missing critical information")
        return False

虽然，最重要的是，你真的应该使用dict ，因为在 list 中搜索是O(n)而在dict中搜索是O(1) ，你的代码也会大大简化。

此外，您不需要返回gamers ，因为您只是附加到它。 您可以返回一个 boolean 来指示插入是否成功。