在Python中从yaml文件动态生成数组元素

Question

Given the following yaml file stored in my_yaml that contains varying sets of dictionary keys and/or class variables (denoted by self._*):

config1.json:
- [[foo, bar], [hello, world]]
config2.json:
- [[foo], [self._hi]]

From the json file, I want to populate a new list of tuples. The items in each tuple are determined by looking up dict keys in this yaml file.

So if I iterate through a dictionary called config1.json , and I have an empty list called config_list , I want to do something like:

config_list.append(tuple[i['foo']['bar],i['hello']['world']])

But if it were config2.json , I want to do something like:

config_list.append(tuple[i['foo'],self._hi])

I can do this in a less dynamic way:

for i in my_yaml['config1.json'][0]:
    config_list.append(tuple([ i[my_yaml[asset][0][0]][my_yaml[asset][0][1]],i[my_yaml[asset][1][0]][my_yaml[asset][1][1]]]))

or:

for i in my_yaml['config2.json'][0]:
    config_list.append(tuple([ i[my_yaml[asset][0][0]],i[my_yaml[asset][1][0]]]))

Instead I would like to dynamically generate the contents of config_list

Any ideas or alternatives would be greatly appreciated.

Answer 1

I think you are bit confusing things, first of all because you are referring to a file in "From the json [ sic ] file" and there is no JSON file mentioned anywhere in the question. There are mapping keys that look like filenames for JSON files, so I hope we can assume you mean "From the value associated with the mapping key that ends in the string .json ".

The other confusing thing is that you obfuscate the fact that you want tuples but load list nested in list nested in lists from you YAML document. If you want tuples, it is much more clear to specify them in your YAML document:

config1.json:
- !!python/tuple [[foo, bar], [hello, world]]
config2.json:
- !!python/tuple [[foo], [self._hi]]

So you can do:

import sys
import ruamel.yaml


yaml = ruamel.yaml.YAML(typ='unsafe')
with open('my.yaml') as fp:
    my_yaml = yaml.load(fp)

for key in my_yaml:
    for idx, elem in enumerate(my_yaml[key]):
        print('{}[{}] -> {}'.format(key, idx, my_yaml[key][idx]))

which directly gives you the tuples you seem to want instead of lists you need to process:

config1.json[0] -> (['foo', 'bar'], ['hello', 'world'])
config2.json[0] -> (['foo'], ['self._hi'])

In your question you hard code access to the first and only element of the sequence that are the values for the root level mapping. This forces you to use the final [0] in your for loop. I assume you are going to have multiple elements in those sequences, but for a good question you should leave that out, as it is irrelevant for the question on how to get the tuples, and thereby only obfuscating things.

Please note that you need to keep control over your input, as using typ='unsafe' is, you guessed, unsafe. If you cannot guarantee that use typ='safe' and register and use the tag !tuple .