pysam

Parse and analyze NGS alignment, variant, and sequence files with pysam.

4|Updated Mar 2, 2026
One-click install
npx skills add https://github.com/shushuzn/Rairos --skill pysam-shushuzn
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: pysam
Source: https://github.com/shushuzn/Rairos/tree/main/skills/pysam
Command: npx skills add https://github.com/shushuzn/Rairos --skill pysam-shushuzn

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

Pysam streamlines NGS analysis by giving a Pythonic interface to read, query, and write genomic alignment, variant, and sequence data without stitching together many separate command-line tools.

Core Features & Use Cases

  • Alignment (SAM/BAM/CRAM) handling: Fetch reads by genomic region, filter by mapping attributes, compute coverage, and run pileup-style analyses for depth and per-position statistics.
  • Variant (VCF/BCF) handling: Iterate and query variants, access INFO/FORMAT fields and genotypes, and filter or write modified VCF/BCF outputs.
  • Sequence (FASTA/FASTQ) handling: Random-access reference FASTA sequences (with indexing) and sequentially process FASTQ reads with quality scores.
  • Integrated workflows: Combine BAM + VCF + FASTA for tasks like validating variants with read support, annotating variants with coverage, and extracting sequence contexts around loci.

Quick Start

Use the pysam skill to compute per-base coverage for chr1 from 1,000,000 to 1,000,500 from a BAM file named tumor.bam.

Frequently Asked Questions about pysam

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I calculate per-base coverage from a BAM file in a specific genomic region?▼

To calculate per-base coverage from a BAM file, use AlignmentFile to fetch reads by genomic region and run pileup-style analyses. This provides depth and per-position statistics for your specified coordinates.

How do I query and filter VCF variants by genotype and INFO fields?▼

To query and filter VCF variants, use VariantFile to iterate variants and access INFO/FORMAT fields and genotypes. You can apply filters and write modified VCF/BCF outputs.

What is the best way to extract FASTA sequences with random access by coordinate?▼

The best way to extract FASTA sequences with random access is by using FastaFile with an indexed reference, enabling programmatic sequence extraction with proper coordinate handling.

Can I integrate BAM, VCF, and FASTA files to validate variants with read support?▼

Yes, you can integrate BAM, VCF, and FASTA files to validate variants with read support. This workflow also allows annotating variants with coverage and extracting sequence contexts around loci.

Do I need indexed files to retrieve reads from a genomic region in SAM or CRAM format?▼

Yes, indexed files are required for retrieving reads from a genomic region in SAM or CRAM format. AlignmentFile relies on indexed random access to fetch reads by coordinates.