[PYTHON] Preserve and read order in PyYAML

Note about PyYAML

When reading a Yaml file with PyYAML, it will be read as a normal Dictionary by default, so The order of the files is not guaranteed.

For example, if you have a Yaml file like this

data.yml

aaa:
  a1: 1
  a2: 2
  a3: 3
bbb:
  b1: 1
  b2: 2
  b3: 3
ccc:
  c1: 1
  c2: 2
  b3: 3

If you normally yaml.load and output

yaml_load.py

import yaml

data = yaml.load(file("data.yml"))

for k1, v1 in data.items():
    for k2, v2 in v1.items():
        print("%s - %s - %s" % (k1, k2, v2))

It looks like this.

Execution result

aaa - a1 - 1
aaa - a3 - 3
aaa - a2 - 2
bbb - b1 - 1
bbb - b2 - 2
bbb - b3 - 3
ccc - c2 - 2
ccc - c1 - 1
ccc - b3 - 3

If you want to read in the order described in the file, read it as OrderedDict.

yaml_load.py

import yaml
from collections import OrderedDict

#Add this
yaml.add_constructor(yaml.resolver.BaseResolver.DEFAULT_MAPPING_TAG,
    lambda loader, node: OrderedDict(loader.construct_pairs(node)))

data = yaml.load(file("data.yml"))

for k1, v1 in data.items():
    for k2, v2 in v1.items():
        print("%s - %s - %s" % (k1, k2, v2))

Now you can keep the order and read.

Execution result

aaa - a1 - 1
aaa - a2 - 2
aaa - a3 - 3
bbb - b1 - 1
bbb - b2 - 2
bbb - b3 - 3
ccc - c1 - 1
ccc - c2 - 2
ccc - b3 - 3

Around here Was referred to

that's all