116 lines
4.5 KiB
Markdown
116 lines
4.5 KiB
Markdown
# Datalite
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[](https://codeclimate.com/github/ambertide/datalite/maintainability)
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[](https://codeclimate.com/github/ambertide/datalite/test_coverage)
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[](https://pypi.python.org/pypi/datalite/)
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[](https://pypi.python.org/pypi/datalite/)
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[](https://datalite.readthedocs.io/en/latest/?badge=latest)
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**THIS PACKAGE IS NOT PRODUCTION READY**
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It should be noted that Datalite is not suitable for secure web applications, it really is only suitable for cases when you can trust user input.
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Datalite is a simple Python
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package that binds your dataclasses to a table in a sqlite3 database,
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using it is extremely simple, say that you have a dataclass definition,
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just add the decorator `@datalite(db_name="db.db")` to the top of the
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definition, and the dataclass will now be bound to the file `db.db`
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[Detailed API reference](https://datalite.readthedocs.io/en/latest/)
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## Download and Install
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You can install `datalite` simply by
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```shell script
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pip install datalite
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```
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Or you can clone the repository and run
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```shell script
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python setup.py
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```
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Datalite has no dependencies! As it is built on Python 3.7+ standard library. Albeit, its tests require `unittest` library.
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## Datalite in Action
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```python
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from dataclasses import dataclass
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from datalite import datalite
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@datalite(db_path="db.db")
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@dataclass
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class Student:
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student_id: int
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student_name: str = "John Smith"
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```
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This snippet will generate a table in the sqlite3 database file `db.db` with
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table name `student` and rows `student_id`, `student_name` with datatypes
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integer and text, respectively. The default value for `student_name` is
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`John Smith`.
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## Basic Usage
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### Entry manipulation
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After creating an object traditionally, given that you used the `datalite` decorator,
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the object has three new methods: `.create_entry()`, `.update_entry()`
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and `.remove_entry()`, you can add the object to its associated table
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using the former, and remove it using the later. You can also update a record using
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the middle.
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```python
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student = Student(10, "Albert Einstein")
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student.create_entry() # Adds the entry to the table associated in db.db.
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student.student_id = 20 # Update an object on memory.
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student.update_entry() # Update the corresponding record in the database.
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student.remove_entry() # Removes from the table.
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```
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But what if you have created your object in a previous session, or wish
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to remove an object unreachable? ie: If the object is already garbage
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collected by the Python interpreter? `remove_from(class_, obj_id)` is
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a function that can be used for this express purpose, for instance:
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```python
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remove_from(Student, 2) # Removes the Student with obj_id 2.
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```
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Object IDs are auto-incremented, and correspond to the order the entry were
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inserted onto the system.
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## Fetching Records
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> :warning: **Limitation! Fetch can only fetch limited classes correctly**: int, float, bytes and str!
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Finally, you may wish to recreate objects from a table that already exist, for
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this purpose we have the module `fetch` module, from this you can import `
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fetch_from(class_, obj_id)` as well as `is_fetchable(className, object_id)`
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former fetches a record from the SQL database given its unique object_id
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whereas the latter checks if it is fetchable (most likely to check if it exists.)
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```python
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>>> fetch_from(Student, 2)
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Student(student_id=10, student_name='Albert Einstein')
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```
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We also have four helper methods, `fetch_range(class_, range_)` and
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`fetch_all(class_)` are very similar: the former fetches the records
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fetchable from the object id range provided by the user, whereas the
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latter fetches all records. Both return a tuple of `class_` objects.
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The last two helper methods, `fetch_if(class_, condition)` fetches all
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the records of type `class_` that fit a certain condition. Here conditions
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must be written is SQL syntax. For easier, only one conditional checks, there
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is `fetch_equals(class_, field, value)` that checks the value of only one `field`
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and returns the object whose `field` equals the provided `value`.
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#### Pagination
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`datalite` also supports pagination on `fetch_if`, `fetch_all` and `fetch_where`,
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you can specify `page` number and `element_count` for each page (default 10), for
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these functions in order to get a subgroup of records.
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