如何在Python中自动向字典添加新值

Question

我正试图编写一种算法，它可以"自动"添加值。当用户输入新东西时，返回到字典。例如…

my_friends = {}
friends = input("What is your friend name?")
#when i type the name, programm should add it itself. Thanks for advices.

Answer 1

friends = {}
def addFriend():
  friends.update({input("What is your friend name?"): None})
addFriend() # asks for the friend...
addFriend() # asks for another friend...
print(friends)

这是一个使用函数的例子，在我们的例子中，它被命名为addFriend。该函数基本上只是使用字典update的内置方法更新friends字典。update获取另一个字典，并使用该字典修改当前字典friends的内容。

假设你在输入中输入了Jessica，它将被存储在friends字典中作为{"Jessica": None}。稍后，您可以通过在字典上执行dict[key]表示法来访问这个添加的键、值对。因此，friends["Jessica"]将等于None，因为在函数中，我们只是将输入字符串添加为键，并将None作为该键的默认值。

希望对你有帮助。

Answer 2

您错过了字典的要点:使用字典必须指定键，例如，您可以使用字典来表示您的"朋友":

friend = {
  'first_name': 'John',
  'last_name': 'Smith',
}

在您的情况下，您想要使用一个列表，使用[]而不是{}创建，然后将输入值附加到您的列表:

my_friends = []
my_friends.append(input("What is your friend name?"))

Answer 3

要在list中添加单个元素，可以使用append()方法。

如果你想用一种更通用的方式来做事情，就像你要求的algorithm which it can add value "automatically"一样，下面是一个解决方案，当然更复杂，但也更通用:

此外，由于您似乎没有使用密钥，因此这是基于list的解决方案:

#You define a function you can use anywhere in your code after
#The function takes the list lst and the string name as inputs
def add_name(lst,name):
    #Here is the append() part. By doing as below, you append name to the end of lst
    lst.append(name)
    #You return your modified list lst
    return lst
#Your empty list of friends
my_friends = []
#Get the friends name from input()
friends = input("What is your friend name?")
#Say your my_friends list is equal to what add_name function returns
my_friends = add_name(my_friends,friends)
#Print
print (my_friends)

输出:

#The add_name function did append the name of your friend to the empty list
['john']

如果你想添加多个好友:

def add_name(lst,name):
    lst.append(name)
    return lst
my_friends = []
#Ask for how many friends you want to add
#Input in always a string so we convert to int for needs below
number = int(input("How many?"))
#You use a for loop with number of iterations equal to number (the How many?)
for i in range(number):
    friends = input("What is your friend name?")
    
    #A new name will be appended each iteration through your function
    my_friends = add_name(my_friends,friends)
    print (my_friends)

关于基础知识的实践培训，我建议:

https://www.w3schools.com/python/ref_list_append.asphttps://www.w3schools.com/python/python_for_loops.asphttps://www.w3schools.com/python/python_functions.asp

Answer 4

my_friends = {}
my_friends["name"] = str(input("What is your friend's name?"))