Multifastats: Multi-Fasta Sequence Stats. Free python-based program that, from a set of a set of 'fasta' sequences (as group or individually), produces basic outputs and statistics (N50, %GC, molecular weight, cut in kmers and concatenate sequences using defined spacers). And also allows to apply some filters and select subgroups by length and/or type. This runs in Windows, Linux and Mac OS.