Python：从评估的字符串列表中循环遍历字典参数的简便方法？

Question

I have a dictionary created from a json file. This dictionary has a nested structure and every few weeks additional parameters are added.

I use a script to generate additional copies of the existing parameters when I want multiple "legs" added. So I first add the additional legs. So say I start with 1 leg as my template and I want 10 legs, I will just clone that leg 9 more times and add it to the list.

Then I loop through each of the parameters (called attributes) and have to clone certain elements for each leg that was added so that it has a 1:1 match. I don't care about the content so cloning the first leg value is fine.

So I do the following:

    while len(data['attributes']['groupA']['params']['weights']) < legCount:
        data['attributes']['groupA']['params']['weights'].append(data['attributes']['groupA']['params']['weights'][0])

    while len(data['attributes']['groupB']['paramsGroup']['factors']) < legCount:
        data['attributes']['groupB']['paramsGroup']['factors'].append(data['attributes']['groupB']['paramsGroup']['factors'][0])

    while len(data['attributes']['groupC']['items']['delta']) < legCount:
        data['attributes']['groupC']['items']['delta'].append(data['attributes']['groupC']['items']['delta'][0])

What I'd like to do is make these attributes all strings and just loop through them dynamically so that when I need to add additional ones, I can just paste one string into my list and it works without having another while loop.

So I converted it to this:

    attribs = [
        "data['attributes']['groupA']['params']['weights']",
        "data['attributes']['groupB']['paramsGroup']['factors']",
        "data['attributes']['groupC']['items']['delta']",
        "data['attributes']['groupD']['xxxx']['yyyy']"
    ]

    for attrib in attribs:
        while len(eval(attrib)) < legCount:
            eval(attrib).append(eval(attrib)[0])

In this case eval is safe because there is no user input, just a defined list of entries. Tho I wouldn't mind finding an alternative to eval either.

It works up until the last line. I don't think the .append is working on the eval() result. It's not throwing an error.. just not appending to the element.

Any ideas on the best way to handle this?

Answer 1

Not 100% sure this will fix it, but I do notice one thing.

In your above code in your while condition you are accessing:

data['attributes']['groupA']['params']['weights']

then you are appending to

data['attributes']['groupA']['params']['legs']

In your below code it looks like you are appending to 'weights' on the first iteration. However, this doesn't explain the other attributes you are evaluating... just one red flag I noticed.

Answer 2

Actually my code was working. I was just checking the wrong variable. Thanks Me! :)