python - Ruamel yaml formatting of dumped nested lists -

i dump dictionary components nested lists, each row of list on own line. want maintain dictionary order.

here's mwe:

import sys  ruamel import yaml ruamel.yaml import yaml  d = {'b':1,      'a':[[1, 2],[3, 4]]}  # desired output: # b: 1 # a: # - [1, 2] # - [3, 4]  print() yaml.dump(d, sys.stdout) print('\n') yaml().dump(d, sys.stdout) 

and here's get:

a: - [1, 2] - [3, 4] b: 1   b: 1 a: - - 1   - 2 - - 3   - 4 

the first method has nested-list formatting want, loses dictionary order. (not surprise since i'm not using round-trip dumper) second method manages maintain order, loses desired nested list formatting. time use round-trip dumper, i've lost nice nested list formatting.

any tips here?

that dictionary has order want either luck, or because using python 3.6. in older versions of python (i.e < 3.6) order not guaranteed.

if targeting 3.6 , have ruamel.yaml>=0.15.32 can do:

import sys  ruamel import yaml ruamel.yaml import yaml   d = {'b':1,      'a':[[1, 2],[3, 4]]}  y = yaml() y.default_flow_style = none y.dump(d, sys.stdout) 

if have older version , python 3.6:

import sys  ruamel import yaml ruamel.yaml import yaml  y = yaml()  d = {'b':1,      'a':[y.seq([1, 2]),y.seq([3, 4])]}   seq in d['a']:     seq.fa.set_flow_style() y.dump(d, sys.stdout) 

to get:

b: 1 a: - [1, 2] - [3, 4] 

to order want in older versions of python consistently should do:

d = y.map() d['b'] = 1 d['a'] = y.seq([1, 2]),y.seq([3, 4]) 

and ruamel.yaml>=0.15.32 can leave out call y.seq().