Question

I’m creating an arbitrary number of instances (using for loops and ranges). At some event in the future, I need to change an attribute for only one of the instances. What’s the best way to do this?

Right now, I’m doing the following:
1) Manage the instances in a list.
2) Iterate through the list to find a key value.
3) Once I find the right object within the list (i.e. key value = value I’m looking for), change whatever attribute I need to change.

for Instance within ListofInstances:
    if Instance.KeyValue == SearchValue:
        Instance.AttributeToChange = 10

This feels really inefficient: I’m basically iterating over the entire list of instances, even through I only need to change an attribute in one of them.

Should I be storing the Instance references in a structure more suitable for random access (e.g. dictionary with KeyValue as the dictionary key?) Is a dictionary any more efficient in this case? Should I be using something else?

Thanks,
Mike

Answer 1

Should I be storing the Instance references in a structure more suitable for random access (e.g. dictionary with KeyValue as the dictionary key?)

Yes, if you are mapping from a key to a value (which you are in this case), such that one typically accesses an element via its key, then a dict rather than a list is better.

Is a dictionary any more efficient in this case?

Yes, it is much more efficient. A dictionary takes O(1) on average to lookup an item by its key whereas a list takes O(n) to lookup an item by its key, which is what you are currently doing.

Using a Dictionary

 # Construct the dictionary
 d = {}

 # Insert items into the dictionary
 d[key1] = value1
 d[key2] = value2
 # ...

 # Checking if an item exists
 if key in d:
      # Do something requiring d[key]
      # such as updating an attribute:
      d[key].attr = val