Question

以下代码仅为第一部分DNA提供结果，“附加”以某种方式不附加且列表未扩展。

DNA= open("Ex72_genomic_dna2.txt", "r")
EXON = open("Ex72_exons2.txt", "r")
DNAST = []
DNAseq = DNA.read()

for li in EXON:
    positions = li.split(',')
    start = int (positions[0]) -1
    stop = int (positions[1])
    # start = 1, stop = 8
    piece = str (DNAseq [start:stop])
    # piece = 'CGATCGT'
    DNAST.append(piece)
    print (DNAST)

NewDNA = DNAST [0]
rangemax = len(DNAST)


if rangemax > 1:
    for num in range (1, rangemax):
        NewDNA = NewDNA + "" + DNAST [num]
DNA.close()
EXON.close()
print (NewDNA)
print ("But should be CGATCGTCCGTCCGATGCCGATCG")
# the Content of Ex72_genomic_dna2.txt: TCGATCGTACCGTCGACGATGCTACGATCGTCGAT
#the Content of  Ex72_exons2.txt:    2,8,10,14,17,22,25,30

Answer 1

我认为问题出现了，因为您认为for li in EXON:会迭代Ex72_exons2.txt文件中的每个项目。执行此操作的正确方法是像以前一样迭代每一行，然后迭代该行中的每个拆分。

这是适合您情况的正确代码：

DNA= open("Ex72_genomic_dna2.txt", "r")
EXON = open("Ex72_exons2.txt", "r")
DNAST = []
DNAseq = DNA.read()

for li in EXON:
    positions = li.split(',')
    for i in range(0, len(positions), 2):
        start = int (positions[i]) -1
        # .strip() because of trailing newline character.
        stop = int (positions[i+1].strip())
        piece = str (DNAseq [start:stop])
        DNAST.append(piece)
        print (DNAST)

NewDNA = DNAST [0]
rangemax = len(DNAST)

if rangemax > 1:
    for num in range (1, rangemax):
        NewDNA = NewDNA + "" + DNAST [num]

DNA.close()
EXON.close()
print (NewDNA)
print ("CGATCGTCCGTCCGATGCCGATCG") # <-- correct output for comparison.

值得指出的是这部分代码：

NewDNA = DNAST [0]
rangemax = len(DNAST)

if rangemax > 1:
    for num in range (1, rangemax):
        NewDNA = NewDNA + "" + DNAST [num]

可以替换为：

NewDNA = ''.join(DNAST)

Answer 2

在您的代码中，for li in EXON:中 li 的值将是EXON的全部内容。即如果Ex72_exons2.txt的文本为“1,2,3,4”，则li为“1,2,3,4”，循环将只迭代一次。来自torrent的解决方案将解决您遇到的问题。

附加到列表失败。仅打印其中一件。如何修复循环？

2 个答案: