How to convert a string to a Python class object?

Converting a string to a Python class means accessing a Python class using its name stored as a string, allowing dynamic creation of objects at runtime. This is useful for factory patterns, plugin systems, and configuration-driven object creation.

Using globals() Function

The globals() function retrieves classes from the global namespace using their string names ?

class Bike:
    def start(self):
        print("Bike started!")

class_name = "Bike"
cls = globals()[class_name]  # Convert string to class
obj = cls()
obj.start()
print(type(obj))

The output of the above code is ?

Bike started!
<class '__main__.Bike'>

Using locals() Function

The locals() function accesses classes from the local scope, such as classes defined inside functions ?

def create_object():
    class Animal:
        def bark(self):
            print("I am an Animal")
    
    class_name = "Animal"
    cls = locals()[class_name]
    obj = cls()
    obj.bark()
    print(type(obj))

create_object()

The output of the above code is ?

I am an Animal
<class '__main__.create_object.<locals>.Animal'>

Using getattr() Function

The getattr() function retrieves classes from imported modules. First, create a file named mymodule.py ?

# mymodule.py
class Tutorialspoint:
    def greet(self):
        print("Hello welcome to Python Tutorial")

Then import and access the class dynamically ?

import mymodule

class_name = "Tutorialspoint"
cls = getattr(mymodule, class_name)
obj = cls()
obj.greet()
print(type(obj))

The output of the above code is ?

Hello welcome to Python Tutorial
<class 'mymodule.Tutorialspoint'>

Using eval() Function (Not Recommended)

The eval() function can dynamically evaluate class names, but it's unsafe for untrusted input ?

class Car:
    def drive(self):
        print("Car is driving")

class_name = "Car"
cls = eval(class_name)  # Security risk with untrusted input
obj = cls()
obj.drive()
print(type(obj))

The output of the above code is ?

Car is driving
<class '__main__.Car'>

Comparison

Conclusion

Use globals() for global classes, locals() for local classes, and getattr() for module classes. Avoid eval() due to security risks with untrusted input.