Convert string to Python class object?

Current namespace utilization

With sys.modules[__name__], access the current namespace and get a class from there.

import sys # Importing sys like it's going out of style

class MyClass:
    # Just a lonely class looking for a reference
    pass 

class_name = "MyClass" 
class_object = getattr(sys.modules[__name__], class_name)() # Get class, not claustrophobia


Using eval() with caution

Before using eval(), validate input. It's like inviting strangers to your house, you need to check them first.

def safe_eval(class_str): # Eval in a bulletproof vest
    if class_str in globals():
        return eval(class_str)()
    else:
        raise ValueError(f"Class {class_str} is not defined.") # Class gone AWOL

# Example usage
try:
    my_obj = safe_eval('MyClass')
except ValueError as e:
    print(e) # Where's Waldo, but for classes


Import modules with style

importlib.import_module() is your best bet for safety and compatibility when dealing with external modules.

from importlib import import_module # Importing modules, not problems

module_name = 'my_module' 
class_name = 'MyClass' 
module = import_module(module_name) 

# Safety checking like your life depends on it
if hasattr(module, class_name):
    MyClass = getattr(module, class_name)
    my_obj = MyClass() # Voila, you've got an object


Handling errors like a pro

Gracefully handle AttributeError and ImportError to prevent class or module related nightmares.

try:
    MyClass = globals()['NonExistentClass']
except KeyError:
    print("Class not found in current module.") # Class playing hide and seek.

try:
    MyClass = getattr(module, 'NonExistentClass')
except AttributeError:
    print("Class not found in the specified module.") # Class on a lunch break.


Structured class retrieval, because we mean business

When it comes to class retrieval, methodology matters. Pass both module and class names as arguments to functions for a clean, reusable, and structured way.

def get_class(module_name, class_name): # Who you gonna call? get_class().
    module = import_module(module_name)
    return getattr(module, class_name) 

# Example usage
MyClass = get_class('my_module', 'MyClass') # Get class, not claustrophobia
my_obj = MyClass() # Voila, you've got an object.


Security considerations when playing with strings

Working with dynamic execution holds potential security risks. So let's tread on this string-landmine carefully.

The risky business of eval()

While eval() is tempting like a cookie jar, untrusted inputs can lead to a mess. Always validate inputs or use safer alternatives like ast.literal_eval().

Clean those dirty inputs

Input sanitization: not as glamorous as Python slaying, but oh so important. Always sanitize and validate your strings to prevent security vulnerabilities.

Framework-specific importing

Tools like Django's import_string provide secure dynamic importing. So when in Rome (or Django in our case)...

Reflections on Python introspection

Python provides a great tool for introspection, the inspect module. It's like a mirror for your code, reflecting objects in a more controlled and predictable manner.