How to Import Class from Another File in Python
Published: 2023-05-29 14:26:50

In programming, it is important to have organized and modular code. Importing classes from another file allows for better organization and structure by separating different components of the code into different files. This also allows for easier maintenance and debugging since changes can be made to a single file without affecting the entire program.

In Python, the import statement is used to import modules, functions, and classes from other files or modules into the current file or module. The basic syntax of the import statement is as follows:


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/uwx5ln51v0dw9dg6cbst.png)


Here, module_name is the name of the module to be imported.

It is also possible to import specific classes or functions from a module using the from keyword. The syntax for this type of import statement is as follows:


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/538hh4fw5v99mzra5a5c.png)


Here, module_name is the name of the module from which the class is to be imported, and class_name is the name of the class to be imported.

How to Import a Class from Another File
To import a class from another file in Python, you first need to create a separate file that contains the class you want to import. Then, in the file where you want to use that class, you can import it using the import keyword followed by the name of the file and the name of the class.

For example, if you have a file called my_class.py that contains a class called MyClass, you can import it into another file using the following code:

from my_class import MyClass
This will allow you to use the MyClass class in your current file, and you can create instances of it and call its methods just like any other class.

Examples of Accessing Class Attributes and Methods
After importing a class from another file, we can access it in the current file by using the class name. To access the attributes and methods of the imported class, we need to create an instance of the class. We can then use this instance to access all the attributes and methods of the class.

For example, suppose we have a file called myclass.py that contains a class called MyClass with an attribute x and a method foo(). In another file, we can import the MyClass class and create an instance of it as follows:

from myclass import MyClass

// create an instance of MyClass
my_instance = MyClass()

// access the 'x' attribute
print(my_instance.x)

// call the 'foo' method
my_instance.foo()
In this example, we first import the MyClass class from the myclass module. We then create an instance of MyClass called my_instance. Finally, we access the x attribute of my_instance using the dot notation (my_instance.x) and call the foo() method using the same syntax (my_instance.foo()).

Once we have imported the class, we can access its attributes and methods using the dot notation. For instance, if we have a class called Person in a file named person.py, and we want to access its name attribute and greet method from another file, we can do the following:

from person import Person

// create an instance of the Person class
person = Person("John")

// access the name attribute
name = person.name

// call the greet method
person.greet()
In this example, we first import the Person class from the person.py file. Then, we create an instance of the Person class and store it in a variable called person. Next, we access the name attribute of the person object using the dot notation and store it in a variable called name. Finally, we call the greet method of the person object using the dot notation.

Importing Multiple Classes from a Single File
In Python, it is possible to import multiple classes from a single file. This can be done by separating the class names with a comma, as shown in the following code:

from my_module import MyClass1, MyClass2, MyClass3
This statement imports MyClass1, MyClass2, and MyClass3 from the my_module module. Once imported, these classes can be used just like any other class.

It is important to note that when importing multiple classes from a single file, each class must be defined in the file with its own class definition. This means that the file should contain something like:

class MyClass1:
    def __init__(self):
        pass

class MyClass2:
    def __init__(self):
        pass

class MyClass3:
    def __init__(self):
        pass
By importing multiple classes from a single file, you can avoid cluttering your code with numerous import statements. This can make your code more readable and easier to maintain.

How to Import Multiple Classes from a Single File Using the from ... import ... syntax
In Python, we can import multiple classes from a single file using the from ... import ... syntax. To do this, we need to list the names of the classes we want to import separated by commas. For example, suppose we have a file named my_classes.py that contains two classes named ClassA and ClassB. To import both classes into another file, we can use the following statement:

from my_classes import ClassA, ClassB
This statement will allow us to use both ClassA and ClassB in our new file without having to import them separately.

Access the Imported Classes in the Current File
To access the imported classes in the current file, you need to first import the module containing the classes using the import statement. Once you have imported the module, you can access the classes using the . operator. For example, if you have a module called my_module which contains a class called MyClass, you can import the class into your current file by using the following code:

from my_module import MyClass
Once you have imported the class, you can create an instance of it using the following code:

obj = MyClass()
You can then access the methods and attributes of the class using the . operator. For example, if the MyClass class has a method called my_method, you can call it using the following code:

obj.my_method()
This will execute the my_method method of the MyClass class.

Rename an Imported Class Using the 'as' Keyword
To rename an imported class using the as keyword, we simply include as followed by the new name we want to give the class after the original class name in the import statement. For example, if we want to import the Person class from a module called person_module and rename it to Human, we can use the following import statement:

from person_module import Person as Human
Now we can refer to the Person class as Human in our code. This is particularly useful when importing classes with long or unclear names, or when we want to avoid naming conflicts with other classes in our program.

How to Use the Renamed Class in the Current File
Once we have renamed the class in the imported file, we can use it in the current file. Suppose we have a class named Employee in a file named employee.py, and we want to import it into another file named main.py. We can first rename the class in employee.py to CompanyEmployee as Employee might conflict with some other class names in the current file. After that, we can import the renamed class using the from statement followed by the file name as shown below:

from employee import CompanyEmployee

employee1 = CompanyEmployee("John", "Doe")
employee1.display_employee()
Here, we have imported the CompanyEmployee class from the employee.py file and created an object of that class. We can now use the object to call the methods of the class, such as display_employee().

How to Import Classes from Another File in a Different Directory
To import a class from another file in a different directory in Python, we need to specify the path to the directory containing the file. We can either use an absolute path or a relative path.

To use an absolute path, we need to specify the full path to the directory containing the file. On the other hand, to use a relative path, we need to specify the path relative to the current directory. Once we have specified the path to the directory, we can import the class using the from keyword followed by the path to the file and the name of the class.

For example, suppose we have a file called my_class.py in a directory called my_directory. To import the MyClass class from this file in another file in a different directory, we can use the following code:

from my_directory.my_class import MyClass
This code imports the MyClass class from the my_class.py file in the my_directory directory.

Use the sys.path.append() function to Add Directories to the Search Path
When working with modules and packages, Python looks for the files to be imported in a list of directories defined in the sys.path variable. By default, this list includes the current working directory and the standard library directories.

However, if your files are located in a different directory, you need to add this directory to the search path. This is where the sys.path.append() function comes in handy. It allows you to add a directory to the sys.path list at runtime, so that Python can find your modules and packages in that directory.


![Image description](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/sdgus6pv45352w36pmbs.png)


When working on large projects, it is common to have code organized across multiple directories. In such cases, it can be challenging to import classes from files in different directories. Here are some examples of how to import classes from files in different directories:

Importing a class from a module in a parent directory
import sys
sys.path.append("..")

from parent_dir.module_name import ClassName
Importing a class from a module in a subdirectory
from subdirectory.module_name import ClassName
Importing a class using the complete path
from full.path.to.module_name import ClassName
By using these examples, it is possible to import classes from files in different directories and organize code more efficiently.

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