list(tags.keys())

[demidovakatya]

Hey, I wanted to ask why you use list(%some_dictionary%.keys()), for example:

for key in list(tags.keys()):

for key in list(tags.keys()):

As far as I'm concerned, you can iterate over keys or values without list()-ing them. Sorry if it's a stupid question, I'm just learning Python.

[dufferzafar]

Hey! @demidovakatya

Actually, It's not a stupid question at all. And you're right in that you can directly iterate over values without explicitly building a list.

Python doesn't allow you to modify a dictionary while iterating it, so rather than iterating over keys of a dictionary, i build a separate list of keys, and iterate over them instead.

If I would've iterated over the keys directly, this line would've resulted in an error, since it modifies the dictionary.

Hope I made it clear :)

[demidovakatya]

Okay, this is how I've translated your code:

for key in list(tags.keys()):

        # by THIS KEY I mean: key in this iteration

        # if frames exists and this key isn't in frames
        if ((frames and key not in frames) 
        # if frames_skip exists and key is in frames_skip
                or (frames_skip and key in frames_skip)
        # if this key's value (tags[key]) is not a TextFrame
                or not isinstance(tags[key], TextFrame)):
        # screw it
            continue

        # if this pattern is in this key's value
        if re.search(pattern, str(tags[key])):
        # replace pattern with some stuff
            sub = re.sub(pattern, repl, str(tags[key]))
        # make it a list  and put it into this key's value
            tags[key].text = [sub]
        # but if sub is False and prune is true
            if not sub and prune:
                # screw this key and its value
                del tags[key]

Now, I don't understand even more things:

• to begin with, you CAN modify dictionaries. You shouldn't do it in a loop link, though;
• when if not sub and prune is false?
• tags[key].text = [sub] - why do you make it?
• if re.search(pattern, str(tags[key])) - what would change if we removed this line?

Thank for your previous answer, I hope my questions would be useful for you as well. :)