How to flatten multilevel/nested JSON?

I used the following function (details can be found here):

def flatten_data(y):
    out = {}

    def flatten(x, name=""):
        if type(x) is dict:
            for a in x:
                flatten(x[a], name + a + '_')
        elif type(x) is list:
            i = 0
            for a in x:
                flatten(a, name + str(i) + '_')
                i += 1
        else:
            out[name[:-1]] = x

    flatten(y)
    return out

This unfortunately completely flattens whole JSON, meaning that if you have multi-level JSON (many nested dictionaries), it might flatten everything into single line with tons of columns.

What I used, in the end, was json_normalize() and specified structure that I required. A nice example of how to do it that way can be found here.