如何在 Python 中为 YAML 文件的特定键添加值？

Question

Recently I would like to work with YAML file even more with my discord.py bot. So I am currently thinking how do I add a value to a specific key in a YAML file. This is my current YAML file:

connected_guilds:
    - 1st_guild_id

And whenever it connects to another guild, it should appears like so:

connected_guilds:
    - 1st_guild_id
    - 2nd_guild_id

etc.

Here is my current code:

        with open('guilds.yaml', 'r+') as guild_add:
            yaml.dump({'connected_guilds'.replace("'", ""): [guild_id]}, guild_add, indent=4)

So basically I think if I should have an if-clause checking if the key already exists and if so, add it below but I'm still confused while implementing that.

I'd be grateful if someone can help!

Answer 1

You are opening, but not reading the file. You create a new list instead of appending to the existing list.

Here's how to do it:

with open('guilds.yaml', 'r+') as f:
  # load the content
  content = yaml.safe_load(f)
  # append the new id to the existing list
  content["connected_guilds"].append(guild_id)
  # reset the position in the file (it's at the end since we read the file)
  f.seek(0)
  # write the updated YAML to the file
  yaml.dump(content, f)
  # throw away any (old) content of the file after the current position,
  # which is at the end of the YAML we just wrote.
  # since we added more content, it's unlikely that there is more content here,
  # but not impossible!
  f.truncate()