code: def combinefiles(filepath):
      
      ## unpack seq files in filepath
      fastqs = glob.glob(filepath)
      firsts = [i for i in fastqs if "_R1_" in i]
  
      ## check names
      if not firsts:
          raise IPyradWarningExit("First read files names must contain '_R1_'.")
  
      ## get paired reads
      seconds = [ff.replace("_R1_", "_R2_") for ff in firsts]
      return zip(firsts, seconds)
docs: Joins first and second read file names