编写python脚本，读取目的基因的genbank格式文件，并输出无回车和空行的fasta文件，命名为gene_seq.fa。 截取序列的cds区，并构建名为“cds_seq.fa”的fasta文件，按照fasta格式打印输出cds区。

编写Python脚本来处理这种任务，我们可以使用biopython库，它是一个强大的生物学计算工具包，特别是用于序列分析。以下是一个简单的示例：

from Bio import SeqIO

# 读取GenBank文件
with open("your_genbank_file.gb", "r") as gb_file:
    records = list(SeqIO.parse(gb_file, "genbank"))

# 创建一个空字典存储每个记录的CDS区
cds_sequences = {}

for record in records:
    # 查找并提取CDS区域
    for feature in record.features:
        if feature.type == "CDS":
            cds_start = feature.location.start.position
            cds_end = feature.location.end.position
            seq_id = f"{record.id}_{feature.qualifiers['locus_tag'][0]}_CDS"  # 使用 locus_tag 作为标识符
            seq = str(record[cds_start:cds_end])

    # 添加到字典，键为ID，值为CDS序列
    cds_sequences[seq_id] = seq

# 将CDS序列写入新的fasta文件
with open("cds_seq.fa", "w") as out_file:
    for seq_id, seq in cds_sequences.items():
        out_file.write(f">{seq_id}\n{seq}\n")

# 将整个基因序列写入另一个fasta文件，去除回车和空行
gene_seqs = [str(record.seq) for record in records]
with open("gene_seq.fa", "w") as out_file:
    out_file.writelines(f">{record.id}\n{seq.strip()}\n" for record, seq in zip(records, gene_seqs))

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