How to set the limit for key and value for the Python Program

Question

How to set the limit for the key and value for the below program. I wrote one python function to add key and values. How to limit the number of keys = 3 and values = 4. Need to ignore the more than 3 keys and 4 values are added.

Is there any thing like below given in program

self.size_key = 3
and self.size_value = 4 or [[] for _ in range(5)] 

sample code

class my_dict(dict):    
    def add(self, key, value):
        #if len(value) < 4 and len(key) < 3:
            self.setdefault(key, []).append(value)

    def remove_key(self, key):
        del self[key]

    def remove_value(self, key, value):
        if value in self[key]:
            self[key].remove(value)

dict_obj = my_dict()
dict_obj.add('key1', 'value1')
dict_obj.add('key2', 'value9')
dict_obj.add('key1', 'value3')
print(dict_obj)  

Answer 1

To do what you want, you would need to use an Ordered Dict. Because dicts do not keep an order outside of a list. It would be impossible to predict which key is getting deleted.

This solves your problem.

from collections import OrderedDict

class my_dict(OrderedDict):
    def add(self, key, value):
        self.check(key)
        self.setdefault(key, []).append(value)

    def check(self, key):
        if len(self.keys()) == 3:
            del self[next(iter(self))]
        if len(self.get(key, [])) == 4:
            del self[key][0]

dict_obj = my_dict()
dict_obj.add('key1', 'value1')
dict_obj.add('key2', 'value9')
dict_obj.add('key1', 'value3')
dict_obj.add('key1', 'value4')
dict_obj.add('key1', 'value5')
dict_obj.add('key1', 'value6')
dict_obj.add('key3', 'value6')
dict_obj.add('key4', 'value6')
print(dict_obj)