Dilawar Singh Being Dilawar/ Tools/

If you want to override [] operator in Python, you may need to handle slice as well. For example in the following __getindex__ method which implements [], argument key could be a single int, for example, a[1] or a[-3]; or it could be a slice e.g., a[1:4] is a slice.

def __getitem__(self, key): 
    x = [1,2,3,4,5,6]  # fixed data
    if isinstance(key, slice): 
        return [x[i] for i in slice2range(slice, len(x)]    
    return x[key]

Ideally, I\‘d have loved if range(key) would automatically turn/cast a slice to the equivalent range. See this question on SO.

The simplest solution, IMO, is the following.

def slice2range(slice, N): 
    return range(slice.start or 0, slice.stop or N, slice.step or 1) 

You can use it inline.

def __getitem__(self, key)
    x = [1,2,3,4,5,6] 
    if isinstance(key, slice): 
        # return a list of values. 
        return [x[i] for i in range(key.start or 0, key.stop or len(x), key.step or 1)] 
    return x[key] # return a value