def split_protein_sequences(input_file, output_file_0_400, output_file_401_1000, output_file_1001):
# 打开输出文件
with open(output_file_0_400, "w") as f_0_400, open(output_file_401_1000, "w") as f_401_1000, open(output_file_1001, "w") as f_1001:
# 读取输入的FASTA文件
for record in SeqIO.parse(input_file, "fasta"):
sequence_length = len(record.seq)