I would like to inherit the OrderedDict class to set up a maximum length to the dict.
I did :
from collections import OrderedDict
class limitedDict(OrderedDict):
def __init__(self, length):
OrderedDict.__init__(self)
self.length = length
But now I don't see which function to overwrite to catch the "adding a key" event. I Googled for a while without finding the answer. Even special functions are not clearly an answer.
Use the dunder method __setitem__ as mentioned in the comments by @AshwiniChaudhary. You need to distinguish overwriting and setting a new key, though.
from collections import OrderedDict
class limitedDict(OrderedDict):
def __init__(self, length):
OrderedDict.__init__(self)
self.length = length
def __setitem__(self, key, value):
if key not in self and len(self) >= self.length:
raise RuntimeWarning("Dictionary has reached maximum size.")
# Or do whatever else you want to do in that case
else:
OrderedDict.__setitem__(self, key, value)
Note that while the update method also allows adding new keys, it calls __setitem__ under the hood, as mentioned in the comments.
If the dictionary exceeds the maximum size you might want to self.popitem(last=False) until it matches the length (last=False for FIFO order, last=True for LIFO order, the default).
