# pybedtools.bedtool.BedTool.set_chromsizes

`BedTool.``set_chromsizes`(chromsizes)

  Prepare BedTool for operations that require chromosome coords.

  Set the chromsizes for this genome. If chromsizes is a string, it will be considered a genome assembly name. If that assembly name is not available in pybedtools.genome_registry, then it will be searched for on the UCSC Genome Browser.

  Example usage:

      >>> hg19 = pybedtools.chromsizes('hg19')
      >>> a = pybedtools.example_bedtool('a.bed')
      >>> a = a.set_chromsizes(hg19)
      >>> print(a.chromsizes['chr1'])
      (0, 249250621)