docs: update dev articles
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Scrapling uses SQLite by default, but this tutorial covers writing your storage system to store element properties there for `adaptive` feature.
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Scrapling uses SQLite by default, but this tutorial shows how to write your own storage system to store element properties for the `adaptive` feature.
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You might want to use FireBase, for example, and share the database between multiple spiders on different machines. It's a great idea to use an online database like that because the spiders will share with each other.
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You might want to use Firebase, for example, and share the database between multiple spiders on different machines. It's a great idea to use an online database like that because spiders can share adaptive data with each other.
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So first, to make your storage class work, it must do the big 3:
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@@ -8,7 +8,7 @@ So first, to make your storage class work, it must do the big 3:
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2. Use the decorator `functools.lru_cache` on top of the class to follow the Singleton design pattern as other classes.
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3. Implement methods `save` and `retrieve`, as you see from the type hints:
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- The method `save` returns nothing and will get two arguments from the library
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* The first one is of type `lxml.html.HtmlElement`, which is the element itself. It must be converted to a dictionary using the function `element_to_dict` in submodule `scrapling.core.utils._StorageTools` to keep the same format and save it to your database as you wish.
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* The first one is of type `lxml.html.HtmlElement`, which is the element itself. It must be converted to a dictionary using the `element_to_dict` function in the submodule `scrapling.core.utils._StorageTools` to maintain the same format, and then saved to your database as you wish.
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* The second one is a string, the identifier used for retrieval. The combination result of this identifier and the `url` argument from initialization must be unique for each row, or the `adaptive` data will be messed up.
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- The method `retrieve` takes a string, which is the identifier; using it with the `url` passed on initialization, the element's dictionary is retrieved from the database and returned if it exists; otherwise, it returns `None`.
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> You can take advantage of the custom-made types for Scrapling and use them outside the library if you want. It's better than copying their code, after all :)
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### All current types can be imported alone like below
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### All current types can be imported alone, like below
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```python
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>>> from scrapling.core.custom_types import TextHandler, AttributesHandler
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>>> somedict_2 = AttributesHandler(a=1)
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```
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Note that `TextHandler` is a subclass of Python's `str`, so all normal operations/methods that work with Python strings will work.
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If you want to check for the type in your code, it's better to depend on Python's built-in function `issubclass`.
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Note that `TextHandler` is a subclass of Python's `str`, so all standard operations/methods that work with Python strings will work.
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If you want to check the type in your code, it's better to use Python's built-in `issubclass` function.
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The class `AttributesHandler` is a subclass of `collections.abc.Mapping`, so it's immutable (read-only), and all operations are inherited from it. The data passed can be accessed later through the `_data` property, but be careful; it's of type `types.MappingProxyType`, so it's immutable (read-only) as well (faster than `collections.abc.Mapping` by fractions of seconds).
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So, to make it simple for you if you are new to Python, the same operations and methods from the Python standard `dict` type will all work with class `AttributesHandler` except the ones that try to modify the actual data.
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So, to make it simple for you, if you are new to Python, the same operations and methods from the Python standard `dict` type will all work with the class `AttributesHandler` except for the ones that try to modify the actual data.
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If you want to modify the data inside `AttributesHandler,` you have to convert it to a dictionary first, like using the `dict` function, and then modify it outside.
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If you want to modify the data inside `AttributesHandler`, you have to convert it to a dictionary first, e.g., using the `dict` function, and then change it outside.
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