How to Serialize NumPy Arrays for Django Context Variables?

NumPy Array JSON Serialization Error

When attempting to save a NumPy array as a Django context variable, an error message may indicate that the array is not JSON serializable.

Explanation:

JSON, a data format for web applications, necessitates data to be in a specific structure for efficient transmission. NumPy arrays, on the other hand, are not inherently compatible with the JSON format, hence the error.

Solution:

To resolve this issue and successfully serialize the array, convert it into a JSON-friendly format before saving it as a context variable. The ".tolist()" method of NumPy arrays provides a straightforward solution:

<code class="python">import numpy as np

a = np.arange(10).reshape(2,5)
b = a.tolist()  # Convert NumPy array to nested lists</code>

Now, the variable b contains the same data in a format compatible with JSON serialization. You can save it as a Django context variable without encountering the serialization error.

Additional Notes:

To deserialize the JSON string back into a NumPy array, use the following steps:

1. Read the JSON file:

   <code class="python">obj_text = codecs.open(file_path, 'r', encoding='utf-8').read()</code>

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2. Load the JSON string:

   <code class="python">b_new = json.loads(obj_text)</code>

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3. Convert the list back to a NumPy array:

   <code class="python">a_new = np.array(b_new)</code>

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With these steps, you can effectively serialize and deserialize NumPy arrays for storing and retrieving data in Django applications.

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