Biopython is a mature open-source project offering Python libraries for computational molecular biology and bioinformatics. It provides tools for sequence analysis, 3D structure handling, interaction with BLAST, ClustalW, and EMBOSS, access to online databases, and statistical learning methods. Biopython is freely available at www.biopython.org under the Biopython license, with documentation and source code. It includes modules for reading/writing sequence files, multiple sequence alignments, and phylogenetic data. The Seq object represents biological sequences, supporting methods like transcription and translation. SeqRecord objects store sequence annotations, while Bio.SeqIO and Bio.AlignIO handle various file formats. Biopython also includes modules for online databases, such as NCBI, ExPASy, and KEGG, and supports tools like BLAST, ClustalW, and EMBOSS. It provides functionality for macromolecular structures, sequence motif analysis, and statistical learning, including Bayesian methods and clustering. The population genetics module supports GENEPOP, SIMCOAL2, and Fst outlier detection. BioSQL is an initiative supported by the Open Bioinformatics Foundation (OBF), enabling data storage and retrieval from SQL databases. Biopython is used in bioinformatics software development and scripting, with a large API and extensive documentation. It is a collaborative effort involving many contributors and is supported by the OBF. Funding comes from the Portuguese Foundation for Science and Technology. No conflicts of interest are declared.Biopython is a mature open-source project offering Python libraries for computational molecular biology and bioinformatics. It provides tools for sequence analysis, 3D structure handling, interaction with BLAST, ClustalW, and EMBOSS, access to online databases, and statistical learning methods. Biopython is freely available at www.biopython.org under the Biopython license, with documentation and source code. It includes modules for reading/writing sequence files, multiple sequence alignments, and phylogenetic data. The Seq object represents biological sequences, supporting methods like transcription and translation. SeqRecord objects store sequence annotations, while Bio.SeqIO and Bio.AlignIO handle various file formats. Biopython also includes modules for online databases, such as NCBI, ExPASy, and KEGG, and supports tools like BLAST, ClustalW, and EMBOSS. It provides functionality for macromolecular structures, sequence motif analysis, and statistical learning, including Bayesian methods and clustering. The population genetics module supports GENEPOP, SIMCOAL2, and Fst outlier detection. BioSQL is an initiative supported by the Open Bioinformatics Foundation (OBF), enabling data storage and retrieval from SQL databases. Biopython is used in bioinformatics software development and scripting, with a large API and extensive documentation. It is a collaborative effort involving many contributors and is supported by the OBF. Funding comes from the Portuguese Foundation for Science and Technology. No conflicts of interest are declared.