pysam

name	pysam
description	Genomic file toolkit. Read/write SAM/BAM/CRAM alignments, VCF/BCF variants, FASTA/FASTQ sequences, extract regions, calculate coverage, for NGS data processing pipelines.
license	MIT license
metadata	{"skill-author":"K-Dense Inc."}
verified	false
lastVerifiedAt	"2026-02-19T05:29:09.098Z"
source	builtin
trust_score	100
provenance_sha	5d44cbd041e49972

Pysam

Overview

Pysam is a Python module for reading, manipulating, and writing genomic datasets. Read/write SAM/BAM/CRAM alignment files, VCF/BCF variant files, and FASTA/FASTQ sequences with a Pythonic interface to htslib. Query tabix-indexed files, perform pileup analysis for coverage, and execute samtools/bcftools commands.

When to Use This Skill

This skill should be used when:

• Working with sequencing alignment files (BAM/CRAM)
• Analyzing genetic variants (VCF/BCF)
• Extracting reference sequences or gene regions
• Processing raw sequencing data (FASTQ)
• Calculating coverage or read depth
• Implementing bioinformatics analysis pipelines
• Quality control of sequencing data
• Variant calling and annotation workflows

Quick Start

Installation

uv pip install pysam

Basic Examples

Read alignment file:

import pysam

# Open BAM file and fetch reads in region
samfile = pysam.AlignmentFile("example.bam", "rb")
for read in samfile.fetch("chr1", 1000, 2000):
    print(f"{read.query_name}: {read.reference_start}")
samfile.close()

Read variant file:

# Open VCF file and iterate variants
vcf = pysam.VariantFile("variants.vcf")
for variant in vcf:
    print(f"{variant.chrom}:{variant.pos} {variant.ref}>{variant.alts}")
vcf.close()

Query reference sequence:

# Open FASTA and extract sequence
fasta = pysam.FastaFile("reference.fasta")
sequence = fasta.fetch(, , )
(sequence)
fasta.close()