谁能告诉我我做错了什么，字典与 Python 中的列表？

Question

I am trying to initialize a dictionary as a attribute in my object and trying to use defaultdict. Somehow, it works on Mac not Windows. What I want is:

1 {'1':[], '2':[]}
2 {'1':[], '2':[]}

Here is what I ve done so far.

class A:
    
    def __init__(self, id):
        self.id = id
        self.x = self.y

    @property
    def y(self):
        ref = defaultdict(list)
        ls = ['1', '2']
        for i in ls:
            ref[i] = []
        return ref

    def __str__(self):
        return f'{self.id}, {self.x}'.format(self=self)

def main():
    for i in range(2):
        me = A(i)
        print(me)

if __name__ == '__main__':
    main()

Error message I'm having is:

KeyError: "'23'" 

or some other numbers and varies every time. The self.y function works when I am just directly accessing it. Like:

    for i in range(2):
        me = A(i)
        print(me.y)

Of course, before that I set:

class A: 
    
        def __init__(self, id):
            self.id = id    
            self.x =  [] 

then

    for i in range(2):     
        me = A(i)
        print(me)

I get

1 []
2 []

but I want

1 {'1':[]}
2 {'2':[]}

so I can add some values in dictionary values.

What am I doing wrong? It seems there is a problem in return values when I sign {} instead of [] . Is there a way to figure out or work around it?

Answer 1

You are using both f"" and str.format , so you do formatting twice. str.format interprets 1 {'1':[]} as template string and tries to expand '1' , thus a KeyError .

Answer 2

Thanks great responses and recommendations. Yes, I am sure many of you see 'weird' stuff in my codes because I do not fully explained the purposes. Yes, I should not use defaultdict instead of a simple dict. Yes, I was using f'' also.format(). Thanks for the lesson.

What works across platform is could be simple but want your feedback. '''

class A:

    def __init__(self, x):
        self.x = x   # id
        self.y = {}  # key = days, value = activities 
    
    def make_day(self):
    ''' each inst accepts random days and days have random activities'''
        random_days =  ['sorted','string','days','sampled','from','week']
        for each_day in random_days:
            self.y[each_day] = []
        return self.y
    
     def __str__(self):
        return f'%d, %s'%(self.x, self.y)

def main(): for i in range(2): a = A(i) a.make_day() print(a) if name == ' main ': main()

0, {'sorted': [], ..., 'week': []} 1, {'sorted': [], ..., 'week': []}

'''