If a Python library is built can it be turned into a research paper? Will it be accepted?
The point of research is the production of knowledge. If, after you take away all the code you’ve written and the datasets you’ve collected, and there’s nothing left, you’re not doing research, you’re doing development.
So, if you want to do artefact-oriented research like this, the question you have to ask yourself is this: what is the new knowledge you’re producing? Are you testing a new, better algorithm? Are you applying an existing algorithm in a new context and determining if it works there? Are you investigating how a complex system functions, or how it interacts with humans and/or the environment? What is the research question that you’re answering?
If you do determine that you’re doing research rather than development, however, there are a number of artefact-oriented research methodologies, however, such as the Design Science Research Methodology. You should be able to find more information on it with Google Scholar, if you’re a member of an institution that gives you access to their research journal subscriptions.
There might be research that leads you to build such a library, but coding itself, isn't research. But compilers, for example, were built on a ton of research prior to any coding beyond the experimental.
One often, in CS, does some research first and then builds something to validate the conclusions of the research. But the paper produced is about the research findings, not the code. Code optimizers fall in this category as do many aspects of operating systems.
But note that it starts with the research, not the code.