How to convert dictionary with numpy array to json and back?

Question

I am learning python development and I am new to the python world, below is my dictionary with values as NumPy array and I want to convert it to JSON, and convert it back to the dictionary with NumPy array from JSON. Actually, I am trying to convert it using json.dumps() but it is giving me an error that says: the object of type ndarray is not JSON serializable

{
  'chicken': array([5. , 4. , 3. , 2. , 1. , 0.5, 0. ]),
  'banana': array([4. , 3. , 2. , 1. , 0.5, 0. ]),
  'carrots': array([5. , 4. , 3. , 2. , 1. , 0.5, 0. ]),
  'turkey': array([5. , 4. , 3. , 2. , 1. , 0.5, 0. ]),
  'rice': array([3. , 2. , 1. , 0.5, 0. ]),
  'whey': array([5. , 4. , 3. , 2. , 1. , 0.5, 0. ]),
  'peanut': array([5. , 4. , 3. , 2. , 1. , 0.5, 0. ]),
  'Yellow Cake (with Vanilla Frosting)': array([5. , 4. , 3. , 2. , 1. , 0.5, 0. ])
}

I am doing this because I want to pass data from one AWS Lambda function to another AWS Lambda function. Any help will be appreciated, Thanks.

Does this answer your question? NumPy array is not JSON serializable — jjramsey
– jjramsey, Commented Jan 27, 2022 at 20:06

mujjiga · Accepted Answer · 2020-12-17 11:18:36Z

numpy arrays cannot be converted into json directly; instead use list.

# Test data
d = {
  'chicken': np.random.randn(5),
  'banana': np.random.randn(5),
  'carrots': np.random.randn(5)
}

# To json
j = json.dumps({k: v.tolist() for k, v in d.items()})

# Back to dict
a = {k: np.array(v) for k, v in json.loads(j).items()}

print (a)
print (d)

Output:

{'banana': array([-0.9936452 ,  0.21594978, -0.24991611,  0.99210387, -0.22347124]),
 'carrots': array([-0.7981783 , -1.47840335, -0.00831611,  0.58928124, -0.33779016]),
 'chicken': array([-0.03591249, -0.75118824,  0.58297762,  0.5260574 ,  0.6391851 ])}

{'banana': array([-0.9936452 ,  0.21594978, -0.24991611,  0.99210387, -0.22347124]),
 'carrots': array([-0.7981783 , -1.47840335, -0.00831611,  0.58928124, -0.33779016]),
 'chicken': array([-0.03591249, -0.75118824,  0.58297762,  0.5260574 ,  0.6391851 ])}

FangQ · Accepted Answer · 2022-01-27 20:03:03Z

0

Please see my solution posted here: https://stackoverflow.com/a/70884973/4271392

it uses a lightweight python module jdata to encode numpy arrays and save binary information, and converts from json back to numpy as well.

answered Jan 27, 2022 at 20:03

FangQ

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