Flattens JSON objects in Python. flatten_json flattens the hierarchy in your object which can be useful if you want to force your objects into a table.
pip install flatten_jsonLet's say you have the following object:
dic = {
"a": 1,
"b": 2,
"c": [{"d": [2, 3, 4], "e": [{"f": 1, "g": 2}]}]
}which you want to flatten. Just apply flatten:
from flatten_json import flatten
flatten(dic)Results:
{'a': 1,
'b': 2,
'c_0_d_0': 2,
'c_0_d_1': 3,
'c_0_d_2': 4,
'c_0_e_0_f': 1,
'c_0_e_0_g': 2}For the following object:
dic = [
{"a": 1, "b": 2, "c": {"d": 3, "e": 4}},
{"a": 0.5, "c": {"d": 3.2}},
{"a": 0.8, "b": 1.8},
]We can apply flatten to each element in the array and then use pandas to capture the output as a dataframe:
dic_flattened = [flatten(d) for d in dic]which creates an array of flattened objects:
[{'a': 1, 'b': 2, 'c_d': 3, 'c_e': 4},
{'a': 0.5, 'c_d': 3.2},
{'a': 0.8, 'b': 1.8}]Finally you can use pd.DataFrame to capture the flattened array:
import pandas as pd
df = pd.DataFrame(dic_flattened)The final result as a Pandas dataframe:
a b c_d c_e
0 1 2 3 4
1 0.5 NaN 3.2 NaN
2 0.8 1.8 NaN NaN
By default _ is used to separate nested element. You can change this by passing the desired character:
flatten({"a": [1]}, '|')returns:
{'a|0': 1}By default flatten goes through all the keys in the object. If you are not interested in output from a set of keys you can pass this set as an argument to root_keys_to_ignore:
dic = {
'a': {'a': [1, 2, 3]},
'b': {'b': 'foo', 'c': 'bar'},
'c': {'c': [{'foo': 5, 'bar': 6, 'baz': [1, 2, 3]}]}
}
flatten(dic, root_keys_to_ignore={'b', 'c'})returns:
{
'a_a_0': 1,
'a_a_1': 2,
'a_a_2': 3
}This feature can prevent unnecessary processing which is a concern with deeply nested objects.
Reverses the flattening process. Example usage:
from flatten_json import unflatten
dic = {
'a': 1,
'b_a': 2,
'b_b': 3,
'c_a_b': 5
}
unflatten(dic)returns:
{
'a': 1,
'b': {'a': 2, 'b': 3},
'c': {'a': {'b': 5}}
}flatten encodes key for list values with integer indices which makes it ambiguous for reversing the process. Consider this flattened dictionary:
a = {'a': 1, 'b_0': 5}Both {'a': 1, 'b': [5]} and {'a': 1, 'b': {0: 5}} are legitimate answers.
Calling unflatten_list the dictionary is first unflattened and then in a post-processing step the function looks for a list pattern (zero-indexed consecutive integer keys) and transforms the matched values into a list.
Here's an example:
from flatten_json import unflatten_list
dic = {
'a': 1,
'b_0': 1,
'b_1': 2,
'c_a': 'a',
'c_b_0': 1,
'c_b_1': 2,
'c_b_2': 3
}
unflatten_list(dic)returns:
{
'a': 1,
'b': [1, 2],
'c': {'a': 'a', 'b': [1, 2, 3]}
}>>> echo '{"a": {"b": 1}}' | flatten_json
{"a_b": 1}
>>> echo '{"a": {"b": 1}}' > test.json
>>> cat test.json | flatten_json
{"a_b": 1}
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