Formatting PyYAML dump() output

Question

I have a list of dictionaries, which I want to serialize:

list_of_dicts = [ { 'key_1': 'value_a', 'key_2': 'value_b'},
                  { 'key_1': 'value_c', 'key_2': 'value_d'},
                  ...
                  { 'key_1': 'value_x', 'key_2': 'value_y'}  ]

yaml.dump(list_of_dicts, file, default_flow_style = False)

produces the following:

- key_1: value_a
  key_2: value_b
- key_1: value_c
  key_2: value_d
(...)
- key_1: value_x
  key_2: value_y

But i'd like to get this:

- key_1: value_a
  key_2: value_b
                     <-|
- key_1: value_c       | 
  key_2: value_d       |  empty lines between blocks
(...)                  |
                     <-|
- key_1: value_x
  key_2: value_y

PyYAML documentation talks about dump() arguments very briefly and doesn't seem to have anything on this particular subject.

Editing the file manually to add newlines improves readability quite a lot, and the structure still loads just fine afterwards, but I have no idea how to make dump method generate it.

And in general, is there a way to have more control over output formatting besides simple indentation?

Answer 1

There's no easy way to do this with the library (Node objects in yaml dumper syntax tree are passive and can't emit this info), so I ended up with

stream = yaml.dump(list_of_dicts, default_flow_style = False)
file.write(stream.replace('\n- ', '\n\n- '))