Dictionary with maximun length, keep last N keys on dictionary, using deque object

DictWithMaxKeys.py

from collections import deque

class DictWithMaxKeys:
    def __init__(self, maxlen, init=None):
        self.maxlen = maxlen 
        self._deque = deque()
        self._dict = {}
        
        if init is not None:
            self._dict.update(init)

    def __getitem__(self, key):
        return self._dict[key]

    def __setitem__(self, key, value):
    	# If key not in dictionary, we have to check did maxlen value exeeded,
    	# and remove the last element from deque, before adding the key
        if key not in self._dict:
            if len(self._deque) >= self.maxlen:
                last_key = self._deque.popleft()
                del self._dict[last_key]
                
            self._deque.append(key)
                
        self._dict[key] = value

    def __delitem__(self, key):
        del self._dict[key]

    def __contains__(self, key):
        return key in self._dict

    def __len__(self):
        return len(self._dict)
    
    def __repr__(self):
        return repr(self._dict)


if __name__ == '__main__':
	
	# Simple test
	d = DictWithMaxKeys(5)

	d['a'] = 1
	d['b'] = 2
	d['c'] = 3
	d['d'] = 4
	d['e'] = 5
	d['f'] = 6

	print(d._dict)

	# Test with all abc letters

	from string import ascii_letters

	e = DictWithMaxKeys(maxlen=5)

	print(e._dict)

	for i, letter in enumerate(ascii_letters):
	    e[letter] = i
	    print(e._dict)