Question

I have a dictionary with a key called ev#### where #### is some number that I do not know ahead of time. There is only one of this type of key in the dictionary and no other key starts with ev.

What’s the cleanest way to access that key without knowing what the #### is?

Answer 1

If there is only one such value in the dictionary, I would say it’s better to use an approach similar to this:

for k,v in d.iteritems():
    if k.startswith('ev'):
        result = v
        break
else:
    raise KeyError()  # or set to default value

That way you don’t have to loop through every value in the dictionary, but only until you find the key, which should speed up the calculation by ~ 2x on average.