JDtI (JDataIntegration) is a Python library for data integration and advanced post-processing of single-cell datasets. JDtI enables basic quality control steps such as control of cells per cluster, number of genes per cell, and more advanced tasks like subclustering, integration, and wide visualization. In this approach, we do not drop the cell information during separate set analyses; instead, we use previous cluster cell lineage information for integrating data based on cluster markers and data harmonization. After integration, it is possible to visualize cell interactions and correlations in many ways, including cell distance, correlations, and more. Despite this, it is also able to conduct DEG analysis between sets, selected cells, or grouped cells, and visualize the results on UMAP, volcano plots, and regression plots comparing pairs of cells. It is very powerful for more advanced analyses focusing on specific issues within the data that may not be discovered in basic analyses. Additionally, JDtI offers many functions for data visualization and processing within clean visual outputs, such as volcano plots, gene expression analysis of different data types, clustering, heatmaps, and more. It is compatible with various sequencing approaches, including scRNA-seq and bulk RNA-seq, and supports interoperability with tools such as Seurat, Scanpy, and other bioinformatics frameworks using the 10x sparse matrix format as input. More details about the available functions can be found in the Documentation and Example Usage section on GitHub.