Recursively Replace Dictionary Values With Matching Key

I'm trying to take a dictionary and find all of the keys that match key and replace their value with replace_value. The dictionaries can in theory be infinitely deep, so it must be

Solution 1:

You have some strange behavior where you are expecting a return but you don't have one. Also your description implies it should replace nested keys, but your code you will miss when a dictionary at the top level does not have the key but at a lower level does. I believe the below code accomplishes what you described:

defreplace_item(obj, key, replace_value):
    for k, v in obj.items():
        ifisinstance(v, dict):
            obj[k] = replace_item(v, key, replace_value)
    if key in obj:
        obj[key] = replace_value
    return obj

EDIT: As @dashiell suggested, moving the top level reassignment after the recursive search/replace avoids the infinite recursion trap of having key exist in the replace_value.

Solution 2:

Here's a functional-style take:

def replace(obj, key, val):
    return {k: replace(valif k == key else v, key, val) 
        for k,v in obj.items()} if isinstance(obj, dict) else obj

It's not efficient in Python (since all values/subdicts are re-created), but demonstrates how to solve your problem without side-effects and without mutating objects.

Solution 3:

defreplace_item(obj, key, replace_value):
    """
    Replaces the dictionary value of key with replace_value in the obj dictionary.
    """if key in obj:
        obj[key] = replace_value

    for k, v in obj.items():
        ifisinstance(v, dict):
            replace_item(v, key, replace_value)

I think this is enough.. no need of extra variables, and in most of the systems, default recursion depth is around 1000, you can change it https://docs.python.org/3/library/sys.html#sys.setrecursionlimit