code: def _bowtie_major_version(stdout):
      
      version_line = stdout.split("\n")[0]
      version_string = version_line.strip().split()[2]
      major_version = int(version_string.split(".")[0])
      # bowtie version 1 has a leading character of 0 or 1
      if major_version == 0 or major_version == 1:
          major_version = 1
      return major_version
docs: bowtie --version returns strings like this:
      bowtie version 0.12.7
      32-bit
      Built on Franklin.local
      Tue Sep  7 14:25:02 PDT 2010