How did you come to decide on Spring Python as your API of choice? Spring works well on Java where there's a tradition of declarative programming; defining your application primarily using XML to control a core engine is a standard pattern in Java.

In Python, while the underlying patterns like Inversion of Control are still apposite (depending on your use case), the implementation chosen by Spring looks like a classic case of something produced by a Java programmer who doesn't want to learn Python. See the oft-referenced article Python is Not Java.

I applaud your decision to introduce order and thoughtfulness to your codebase, but you may wish to evaluate a number of options before making your decision. In particular, you may find that using Spring Python will make it difficult to hire good Python programmers, many of whom will run the other way when faced with 1000-line XML files describing object interactions.

Perhaps start by re-examining what you really want to accomplish. The problem cannot simply be that "you need a framework". There are lots of frameworks out there, and it's hard to evaluate a) if you truly need one and b) which one will work if you haven't identified what underlying software problems you need to solve.

If the real problem is that your code is an unmaintainable mess, introducing a framework probably won't fix the issue. Instead of just messy code, you'll have code that is messy in someone else's style :-) Perhaps rigour in the dev team is where you should recommend starting first: good planning, code reviews, stringent hiring practices, a "cleanup" release, etc...

Good luck with the research.

Dependency injection frameworks are not nearly as useful in a dynamically typed language. See for example the presentation Dependency Injection: Vitally important or totally irrelevant? In Java the flexibility provided by a dependency injection framework is vital, while in Python it usually results in unneeded complexity.

This doesn't mean that the principles are wrong. See this example how to achieve loose coupling between classes by using simple idioms:

# A concrete class implementing the greeting provider interface
class EnglishGreetingProvider(object):
    def get_greeting(self, who):
        return "Hello %s!" % who

# A class that takes a greeting provider factory as a parameter
class ConsoleGreeter(object):
    def __init__(self, who, provider=EnglishGreetingProvider):
        self.who = who
        self.provider = provider()
    def greet(self):
        print(self.provider.get_greeting(self.who))

# Default wiring
greeter = ConsoleGreeter(who="World")
greeter.greet()

# Alternative implementation
class FrenchGreetingProvider(object):
    def get_greeting(self, who):
        return "Bonjour %s!" % who
greeter = ConsoleGreeter(who="World", provider=FrenchGreetingProvider)
greeter.greet()