Issues with JSON Date Handling in Python 3.9 when using Flask and Marshmallow
Could someone explain I'm running into a frustrating issue when trying to serialize and deserialize dates in JSON using Flask and Marshmallow with Python 3.9. I have a model with a date field, and when I serialize it, the date is being returned in a format that doesn't match what I expect. Here's a simplified version of my code: ```python from datetime import datetime from flask import Flask, jsonify from flask_marshmallow import Marshmallow app = Flask(__name__) ma = Marshmallow(app) class User: def __init__(self, name, created_at): self.name = name self.created_at = created_at class UserSchema(ma.SQLAlchemyAutoSchema): class Meta: fields = ('name', 'created_at') user = User('Alice', datetime(2023, 10, 1, 15, 30, 0)) user_schema = UserSchema() @app.route('/user', methods=['GET']) def get_user(): return jsonify(user_schema.dump(user)) if __name__ == '__main__': app.run() ``` When I hit the `/user` endpoint, the output looks like this: ```json { "name": "Alice", "created_at": "2023-10-01T15:30:00" } ``` However, I need the `created_at` field to be formatted as `"2023-10-01 15:30:00"` (with a space instead of a `T` between the date and time). I've tried overriding the serialization method in my schema like this: ```python @ma.post_load def format_date(self, data, **kwargs): if 'created_at' in data: data['created_at'] = data['created_at'].strftime('%Y-%m-%d %H:%M:%S') return data ``` But the date is still being returned in the ISO format. I've also checked the Flask and Marshmallow documentation for any options related to date formatting, but I couldn't find anything that directly addresses this issue. Does anyone have any insights on how to achieve the desired date format in the JSON response? I'd really appreciate any help! My team is using Python for this desktop app. Thanks, I really appreciate it!