SHELVE IN PYTHON 2023
SHELVE IN PYTHON Simply put, we can store variables in our python programs in shelf binaries.
What is Shelve SHELVE IN PYTHON methood 1 :
Thus, Shelve in Python is used as a simple persistent storage for arbitrary Python objects that can be loaded using a dictionary-like API.
In Python, we use the Shelve module to help implement persistent storage. Creates a file similar to a dbm database on UNIX-like systems. In this special dictionary object, only the string data type can be used as the key, while any loadable object can serve as the value. The shelf is therefore accessible with a key, just like in a dictionary.
To create a new shelf What is Shelve :
We simply use Shelve through the Dbfilenameshelf class. It uses the anydbm class to store data. Or simply, we can use the shelve.open() function.
First, we import our shelf module
import shelves
The easiest way to create a Shelf object is to use the open() function defined in the Shelf module, which returns a DbfilenameShelf object.
open(filename, flag=’c’, log=None, writeback=False)
The filename parameter is assigned to the created database.
The default value of the flag parameter is “c” for read/write access, “w” (write only) “r” (read only) and “n” (new with read/write).
The protocol parameter indicates the pickle protocol, and the writeback parameter is false by default. If writeback is set to true, the accessed items are cached.
Now we’ll use the open() function to simply open a binary .db file. The name can be anything of our choice, so for example I use data_shelve as the name of my file.
data = shelve.open(‘data_shelve.db’)
Next, we now give the key along with the values using our variable name. Let’s say we put in information about a person, their name, age and email address.
data[‘Name’] = “John Wick”
data[‘Age’] = 32
data[‘Email’] = [email protected]
The data has been written to the shelf file. Now let’s close the file we opened using the close() function.
data.close()
Closing the file is important for the following reasons SHELVE IN PYTHON 2023:
If a file is opened to perform any operation, it is locked from being opened by any other source until the process itself closes it.
The operating system controls the number of files open by a program, so closing files after use allows you to stay within this limit.
Now to access the value of a specific key in the shelf file. We open the file again SHELVE IN PYTHON 2023
data = shelve.open(‘data_shelve.db’)
After opening the file, we have access to any key.
print(data[‘Name’])
so the output will be:
John Wick
Which is the name we put in our shelf file.
Likewise, we can access any key we want. For example:
print(data[‘Age’]
print(data[‘Email’])
and the outputs will be the values we input.
32
[email protected]
We can simply use dictionary functions here because the data we have stored is similar to a dictionary in data structure.
We can use items(), keys() or values() here.
print(data.items())
print(data.values())
print(data.values())
so they will give results like:
[(‘Name’, ‘John Wick’), (‘Age’, 32), (‘Email’, ‘[email protected])
[‘Name’, ‘Age’, ‘Email’]
[‘John Wick’, 32, ‘[email protected]’]
Some other functions like update() can be used to add keys and values to our shelf file.
conclusion:
We learned about the Shelve module, which provides a convenient mechanism for storing persistent dictionary objects SHELVE IN PYTHON 2023.
What is Shelve
We all have come across so many instances in our daily life where we need to use a database management system to store all the required information and data. Using a database management system is often very simple, but sometimes it is a bit difficult when we have to store complex structured data. Database management systems are of different types,
but the most common type that we usually use in our daily life is relational database management system (RDBMS). RDBMS is an effective tool and management system where we can store all our necessary information and data and manage them very easily. There are many cases where we do not need to use a relational database management system or it is not possible to use an RDBMS to store data. In such cases, some questions come to mind: are there any other alternatives in this situation, are there other methods or tools for data storage, etc.
The answer to these questions is Yes! We have other tools and methods that we can use to store data when we don’t need to use the RDBMS method. We have other tools, and many of these tools are tied to the programming language library SHELVE IN PYTHON 2023.
This means that there are libraries in the programming world that provide efficient tools that can be used when it is not possible to use a relational database management system. This thing is also applicable to Python and in Python we have libraries through which we can store all our important data by creating a DBMS like interface.
One such library or module in Python is the Shelve Module, a powerful tool for storing or persisting data. We will learn about this Shelve Module of Python in this tutorial where we store data inside using Shelve Module in Python program SHELVE IN PYTHON 2023.
The Shelve module in Python
Shelve Module of Python is a very popular Python module that works as an efficient tool for persistent data storage inside files using Python. As the name of this module suggests,
it will act as a shelf object that will hold all our data in a file and store all the necessary information. A shelf object is defined in the Shelve module, which behaves like a dictionary object and is permanently
stored in a file on our computer’s disk. This way we can store all the data and information through Python Shelve Module in our system and keep it as long as we want SHELVE IN PYTHON 2023.
Shelf module: Introduction
Shelve Module of Python is a powerful tool by which we can store all data and information in a file and keep it in our computer storage until we change our mind to delete it. Shelve Module is not only useful in storing information in a file but also very efficient in modifying the already present information and adding some new information in the same file SHELVE IN PYTHON 2023.
We can do all these operations (creating, reading, writing and deleting from a file) from the Shelve module using this module and its functions in Python. The Shelve Module creates a file very similar to a DBMS database on systems such as UNIX. As keys, we can only use the string data type in a special dictionary object present in the file, while as values for the keys, objects that can be selected from shelf files can be used.
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Shelf Module: Classes
Like any other Python module, some classes are also present in Shelve module in Python and we will talk about these classes in this section. The following three classes are defined in the Python Shelve module SHELVE IN PYTHON 2023:
No. Module class description
1 Shelf class The shelf class is the base class from the shelf module and is used to implement the shelf in the shelf binder. We can initialize the Shelf class from the Shelve module using a dict-like object inside a Python program SHELVE IN PYTHON 2023.
2 DBFileNameShelf Class This is a subclass of the Shelf base class and accepts the name of the shelf files as a parameter to its constructor rather than a dict object parameter.
3 BsdDbShelf Class The BsdDbShelf class is also a subclass from the shelf base class, and this class accepts a dict-like object as a parameter that distinguishes this subclass from the DBFileNameShelf class. The dict object parameter that we pass as a parameter to its constructors should support the first(), last(), previous(), next(), and set_location() methods SHELVE IN PYTHON 2023.
Now here we have described all the classes and subclasses present in the Shelve module and also learned which type of object is taken as a parameter in these classes.
Working with the shelf module
Shelve Module is a built-in Python library and this module can be found pre-installed in all versions of Python 2 and 3. Therefore, to work with Shelve Module, we don’t need to use any installer or pip command to install shelf module first. We can directly use the ‘import Shelve’ command in a Python program to import and use all the features of the Shelve module in that program SHELVE IN PYTHON 2023.
To understand how the Shelve module works, we will divide its implementation part into three parts, where we first create a Shelve file and store data in it, then open the file and read values from it, and finally update the data in the shelf file. We will learn how to work and implement the Shelve module using the following three steps SHELVE IN PYTHON 2023:
SHELVE IN PYTHON 2023 Create a shelf file for data storage
Loading data from a Shelve file
Updating the data in the Shelve file
We will learn about each of the three parts mentioned above using an example program, where we perform the relevant tasks using the functions of the Shelve module. We will now learn how to implement each part of the Shelve module’s work by first creating a Sample Shelve file.
To create a shelf file for data storage:
If we want to store some data in a shell file, we have to create it first and only then we can add the required data. We can create a Shelve file simply by using its open() function, which works similar to the open() function we use during the file manipulation process. With the open() function of the Shelve module, we need to follow the syntax below when opening or creating a new Shelve file SHELVE IN PYTHON 2023:
>> shelf = open(NameOfFile, flag = ‘c’, protocol = None, writeback = True)
Returns a shelf object from a subclass of DbfilenameShelf where the object will collect data from the user to be saved to a file. The following is a description of the parameters used in the open() function syntax above SHELVE IN PYTHON 2023:
NameOfFile: This is the name of the file we want or have associated with the database (shelf file) we are creating/opening with open() SHELVE IN PYTHON 2023
flag: The flag parameters for the open() function syntax are c, w, n, and r, where ‘c’ is the default. The keyword “c” in the flag parameter represents that we have given read and write access to the file, “w” means that we have given only write access, “r” means that we have given only read access, and “n” represents that we are creating a new file SHELVE IN PYTHON 2023
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