Find Unique Characters in a File

Question

I have a file with 450,000+ rows of entries. Each entry is about 7 characters in length. What I want to know is the unique characters of this file.

For instance, if my f

Answer 1

This answer above mentioned using a dictionary.

If so, the code presented there can be streamlined a bit, since the Python documentation states:

It is best to think of a dictionary as an unordered set of key: value pairs, with the requirement that the keys are unique (within one dictionary).... If you store using a key that is already in use, the old value associated with that key is forgotten.

Therefore, this line of the code can be removed, since the dictionary keys will always be unique anyway:

    if character not in letters:

And that should make it a little faster.