jsonbeautyfier.py

__json = """{
    "test": 123
}"""

max_index = 0
for x in __json.split("\n"):
    index = x.find(":")
    if index > max_index:
        max_index = index

print(max_index)
for x in __json.split("\n"):
    index = x.find(":")
    diff = max_index - index
    try:
        split = x.split(":")
        print(split[0] + " " * diff + ":" +  split[1])
    except IndexError:
        print(x)