Numeric keys in YAML files

Question

Is there any way to stringify numeric keys in a YAML file? I have a sample input file as so:

foo: bar
123: New York
food: Cheese
23.61 : max_value

I'm using the ruamel package to process my files - is there anything available in the loading or dumping calls that could perform the conversion so it would look like:

foo: bar
'123': New York
food: Cheese
'23.61' : max_value

or even all the keys ...

'foo': bar
'123': New York
'food': Cheese
'23.61': max_value

I looked through the API but couldn't see anything obvious ...

Answer 1

There is no loading option that makes all keys strings, but you can do that after loading with a small recursive function:

import sys
import ruamel.yaml

yaml_str = """\
foo: bar
123: New York
food: Cheese
23.61 : max_value
"""

def keys2string(d):
    if isinstance(d, dict):
        for idx, k in enumerate(list(d.keys())):
            if not isinstance(k, str):
                sk = str(k)
                d.insert(idx, str(k), d.pop(k))
                k = sk
            keys2string(d[k])
    elif isinstance(d, list):
        for e in d:
            keys2string(e)


yaml = ruamel.yaml.YAML()
yaml.preserve_quotes = True
data = yaml.load(yaml_str)
keys2string(data)
yaml.dump(data, sys.stdout)

which gives:

foo: bar
'123': New York
food: Cheese
'23.61': max_value

The use of .insert() is one possible way of preserving the order of the keys (i.e. have the stringified keys be in the place of their original numeric keys).