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:
-
Read the JSON file:
<code class="python">obj_text = codecs.open(file_path, 'r', encoding='utf-8').read()</code>
-
Load the JSON string:
<code class="python">b_new = json.loads(obj_text)</code>
-
Convert the list back to a NumPy array:
<code class="python">a_new = np.array(b_new)</code>
With these steps, you can effectively serialize and deserialize NumPy arrays for storing and retrieving data in Django applications.
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