编写fastq质控代码

以下是一个简单的Python代码示例，用于对FASTQ文件进行质量控制。

def quality_control(fastq_file, threshold):
    with open(fastq_file, 'r') as f:
        line_num = 0
        while True:
            line_num += 1
            line1 = f.readline().strip()
            line2 = f.readline().strip()
            line3 = f.readline().strip()
            line4 = f.readline().strip()
            
            if not line4:
                break
            
            quality_scores = [ord(char) - 33 for char in line4]
            average_quality = sum(quality_scores) / len(quality_scores)
            
            if average_quality < threshold:
                print(f"Low quality sequence found at line {line_num}")
                print(f"Average quality: {average_quality}")
                print("Sequence:")
                print(line2)
                print("Quality:")
                print(line4)
                print()

使用示例：

fastq_file = "sample.fastq"
threshold = 30
quality_control(fastq_file, threshold)

上述代码将打开指定的FASTQ文件，并逐行读取文件内容。然后，它将解析每个序列的质量行，并计算平均质量。如果平均质量低于设定的阈值，则将打印出相应的序列及其质量信息