This content originally appeared on DEV Community and was authored by Adwaith Rajesh
Let's see how we can store python objects, this include strings, list, function, etc.., inside a DB like pysonDB
Consider I've function foo which takes an argument x and return x * (x + x). Which I want to store inside a DB.
def foo(x: float) -> float:
return x * (x + x)
First things first we nee to convert this object to byte string. To do that we can use the pickle. module.
import pickle
byte_string = pickle.dumps(foo)
This byte string cannot be directly added to a PysonDB database, as byte strings are not JSON serializable. So a simple workaround will be to add quotes around the byte string which can be easily done like this.
obj_string = f"{byte_string}"
This string can be now added to the DB
from pysondb import db
a = db.getDb("test.json")
a.add({
"name": "foo_function",
"obj": obj_string
})
To get the object back we can do the following steps.
data = a.getBy({"name": "foo_function"})
Now data will look something like this.
[{'name': 'foo_function', 'obj': "b'\\x80\\x04\\x95\\x14\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x8c\\x08__main__\\x94\\x8c\\x03foo\\x94\\x93\\x94.'", 'id': 316182400052721056}]
To convert the obj string back to a callable function. We can do the following.
str_obj = data[0]["obj"]
Remember that str_obj is still a string and not a byte string, which is what we need, since the required byte string is inside this string, we can simply evaluate the string.
import ast
byte_obj = ast.literal_eval(str_obj)
To call the function we can do this.
call_obj = pickle.loads(byte_obj)
print(call_obj(3))
# output
18
Entire Code
import ast
import pickle
from pysondb import db
def foo(x: float) -> float:
return x * (x + x)
byte_string = pickle.dumps(foo)
obj_string = f"{byte_string}"
a = db.getDb("test2.json")
a.add({
"name": "foo_function",
"obj": obj_string
})
data = a.getBy({"name": "foo_function"})
str_obj = data[0]["obj"]
byte_obj = ast.literal_eval(str_obj)
call_obj = pickle.loads(byte_obj)
print(call_obj(3))
So we have successfully stored a python object inside a DB. The steps are the same for all the objects like list or dict.
This content originally appeared on DEV Community and was authored by Adwaith Rajesh
Adwaith Rajesh | Sciencx (2021-06-13T02:14:27+00:00) Storing python objects inside PysonDB. Retrieved from https://www.scien.cx/2021/06/13/storing-python-objects-inside-pysondb/
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