Python字符串索引/打印錯誤

Question

試圖讓DNA閱讀腳本正常工作，現在只是部分。這需要一串'A'，'T'，'C'或'G'字符，並根據子字符串是以'ATG'開始並以'TAA'，'TGA'，'TAG' 。 printAllGenes（）在找到的每一行上打印出一個dna鏈（標識的子串），並通過輸入字符串繼續，直到找不到更多。看起來printAllGenes（）由於findStopCodon（）的else子句中的錯誤而無法完成執行。

gene_sequence = 'AACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTAACCCTCACCCTTCTAACTGGACTCTGACCCTGATTGTTGAGGGCTGCAAAGAGGAAGAATTTTATTTACCGTCGCTGTGGCCCCGAGTTGTCCCAAAGCGAGGTAATGCCCGCAAGGTCTGTGCTGATCAGGACGCAGCTCTGCCTTCGGGGTGCCCCTGGACTGCCCGCCCGCCCGGGTCTGTGCTGAGGAGAACGCTGCTCCGCCTCCGCGGTACTCCGGACATATGTGCAGAGAAGAACGCAGCTGCGCCCTCGCCATGCTCTGCGAGTCTCTGCTGATGAGAACACAGCTTCACTTTCGCAAAGGCGCAGCGCCGGCGCAGGCGCGGAGGGGCGCGCAGCGCCGGCGCAGGCGCGGAGGGGCGCGCCCGAACCCGAACCCTAATGCCGTCATAAGAGCCCTAGGGAGACCTTAGGGAACAAGCATTAAACTGACACTCGATTCTGTAGCCGGCTCTGCCAAGAGACATGGCGTTGCGGTGATATGAGGGCAGGGGTCATGGAAGAAAGCCTTCTGGTTTTAGACCCACAGGAAGATCTGTGACGCGCTCTTGGGTAGAGCACACGTTGCTGGGCGTGCGCTTGAAAAGAGCCTAAGAAGAGGGGGCGTCTGGAAGGAACCGCAACGCCAAGGGAGGGTGTCCAGCCTTCCCGCTTCAACACCTGGACACATTCTGGAAAGTTTCCTAAGAAAGCCAGAAAAATAATTTAAAAAAAAATCCAGAGGCCAGACGGGCTAATGGGGCTTTACTGCGACTATCTGGCTTAATCCTCCAAACAACCTTGCCATACCAGCCCATCAGTCCTCTGAGACAGGTGAAGAACCTGAGGTCGCAGGAGGACACCCAGAAGGTCCAGAGAGAGCCTCCTAGGCCCCCCACCTCCCCCCGTGGCAGCTCCAACCCCAGCTTTTTCACTAGTAAGGCAGTCGGGCCCCTGGGCCACGCCCACTCCCCCAAGCGGGGAAGGAGCTTCGCGCTGCCGCTTGGCTGGGGACTGGGCACCGCCCTCCCGCGGCTCCTGAGCCGGCTGCCACCAGGGGGCGCGCCAGCGGTGTCCGGGAGCCTAGCGGCGCGTGTGCAGCGGCCAGTGCACCTGCTCTGGCCCTCGCCGCGGTCTCTGCCAGGACCCCGACGCCCAGCCTGACCCTGCCATTCAGCGGGGCTGCGGCTCCACGGCCTGCGACAGCAGCCCCACCTGGCATTCAGCGCGCTCCCGGGGGCAGAGGTCGCGGTGTCCTCACGCTGTGGTGCCGGCCTACAACCCCCACGCCGGGCTCGGGCCCGGCGGAGGAGGGCGATGCTCCCCGGGTAGGACAAACCGGTCACCTGGGCTGCGACGGCGGCTTAGGGGCAGAAGCGGCGGTCCAGGGCCGCCTGGCGCAGCAGCCTGTCCCAGCCGCGGTCCCTGCAGTCCCTCCCTGGCGGCTGCGCAGCCGTCCCACGACAGGGGCCATAAACTCTCCAGAGCGGAAAGCCGCACCCTGGTGGCCCGGCCCCGCGCCCAGACCTGGCGGCCGCTGGCACCTGACCCGCTGCATGGGTCTCCAGGGAGCTCGCTGCCCACCCGGCGCTGCAGGCTCGGCTCCCTCGTACACTCTCTGGTAGGTGCTAGGGACGACCCTATGGGCCAGCTTGCCATGCCCAGTCCCCAGGCCGCACCCACCCTGGCTCCCTGGGCTAGGGGACTGGCTCCTCCTGTGAGTCGTGGGTCTGGGAGGCAGGGGCGTTAGGGGAGAGTGAGGGACCGAGGGCAGCCCCTGCTGTGTGCACAGCGAGGTCGTGCACAGGCGTCTGTTGCAGAGCGTGCAGCTTCAGATGAGACTGGATTGCAGGTGGAGATGACTGTGGGTGCGCACACCTGGAGGTGAAGGGGAGGCAGCCTGTCTACCTGACCCATGAAATACAGGAGACTGTACCCCAGAAGCAGCGGGTTCACTGCTCCATTGATTAAGCAAGTCTGGGACACACATGTAGCTAAGCTGTGAGTTCTGTACCAGCGATCCCAACACCCACGCCCTCAGAAAGACACTGGTGTGGGGCCTGGGTGCTTGTCAGGCCTGAAAGTGGAGAGCACGGGCCAGAGACACTGAGTAGGGGGAACCCACCCTAGGGCTCTGAGGGACGACGATGTGGGGAGCTGGTGACAGAGCCTGAGCTGGCCCAATGTTGCACGGTGGGGACAGATTCGAGGTACAGTGGGGACTGGTGACCTCAGTTCCCAGTGTCCCAGCCTGGCCTCCCAGTCCACCCAGCAATTAGTGGGTGCTGCCCTGCAAAGACTCTGGGGGTGCCTCAGCCCTCCTCATCACACGTGACTGGTGACTTCTGTGTCCACCCGCACAATAAGAGGGATCTTCTCTCACTTTCAGGCAAGCCCAAGAAAGTCAGGGGCCTATGTGAGCCAAAGAGGAGAGAAGGTGATGCCTCAGCCCAGTGTTTCTGCCCCACCTCGCTTGTGGCCTTCGGAACTTGATTTGCACCGCAGGAAAATGGGCAATGAAAACCCCTCCCTAACTGGCTTCTCAGTCCACTCTGACCAGCCCACTGCACAGCGCCCACCCTGCAGCTCCAGGTACAGAGGCTGGGATGGCTCTGGGCTGACCTAAGGGCCTTCTGATGGCTCCAACCCTCGGGATGCCTCATGCTCACCCTTTGGCACCCACCTGACAGCTCAGCATCTCTGCTCTCTGCCATCCTCAATGCCTGCTCTAGACAAGCCCAAGTCCCCCAGGAGTGGCAGAGGGAACTGAGCCGAAAACTAAGTCTCGGCTCACTGAACCCCAAGTGGGCTGTCCAGCCTCGCCCTTCAGTTCACAACCCCAGGCAGGTTCCCTCCAGGGATGTGATCCCAGGGGCCACAGCAGCACATTCTGGCCTAACCTATCCACTATTTAAACAGTTACTGAAAAGGCCAGGATGGCCGTGGGCCCTGACATTAATCCCCTTTCTCTGTGAGGGGGCTGGGTTGGGTTTGCCATCCTGATGTCTTTGTGGAAAGAGCTGGCAGGTGAAGCAAGTCTCAGGGGCCAGCCATGGGACAAGGAACCTAGGACTGGCCTCTGCTGGAACCCTCTGAGGCCCCTGCGGACAGGAGGATCCAATGGAGGTCTAGCCACCCCTCCCAGGTTGGTGCTCACAGCCCCTCCCTGGCCCACTCCCTGCACACCTGCACCTGCTGGTCTCTGGGAGAGGAGCATCCATCCATCTTGTGCGCATAGCTTTCGGCTCCATTTTCATGAGGATGGTCTCCTTGGCAGAAATGCCCATTAGGGGATCCTGAGCCTGTGCTAGCTCTTCTCTAAGTGCCAAAGCCAGTGAGAGGGACTTGAAAACTCAAGACTTATTAACAGTATTTTCTGCATTTTGTGCTTTCAGGGTTGTTTTTTCCTTAAAATGTGTAAAAACAAACATTGAGATTTCTATCTTTTATATAATTTGGATTCTGTTATCACACGGACTTTTCCTGAAATTTATTTTTATGTATGTATATCAAACATTGAATTTCTGTTTTCTTCTTTACTGGAATTGTTAACTGTTTTATAGGCCAAATCTTTTAAAAAAAACACATCTCTCTAATTTCTCTAAACATTTCTAATTACATATATATTTACTATACCTAATACACTACTTTGGAATTCCTTGAGGCCTAAATGCATCGGGGTGCTCTGGTTTTGTTGTTGTTATTTCTGAATGACATTTACTTTGGTGCTCTTTATTTTGCGTATTTAAAACTATTAGATCGTGTGATTATATTTGACAGGTCTTAATTGACGCGCTGTTCAGCCCTTTGAGTTCGGTTGAGTTTTGGGTTGGAGAATTTTCTTCCACAAGGGATTGTCTTGGATTTTTCTGTTTCTCCCTCAATATCCACCTGGAAAACATTTCAATTAATTTATATTTACTTAAATATTTCTGTGCAAAAACTGTGTACAAAAGCCCCAAAGCATAATTTGTGCAGTTGAGCGCATGTTCTGTTGTTCAGCATTTATGGTGGTTGGTAGTGGAAAAGATTTTTAGAATATGTGGATTTTCGGGATATTCCCAGAAGCCCAGATAGCGACACTTTACCTTTGGAGGAATTACTTCTCAGAATATTGCACACAATCAATCGCCTTTGGAAGGAGCATATATCCCCAGCAAAAGCTCTGGTTTTTTGAAGTCTGTATTGTGTGTTACTTCCAGGAGAATATGCAATGATGACAATGTTATTAGATGATTCAAATATGAAGTGCTGTTATGCCAAACAATGAATCTTTGTGTTATACATTATGCCTAACTATAAATCTTTGTGTTATACATTTTAATGTCATTGGAGAGTACTCCTGTCTTCTTGGCATTATTGATAATTAGATTCTAATTGCTAATAAGTCAGAAAAATTAGGAACACCAAATTTCAGTTGTCTCAAAAGCACTCCTCTTATTAAATTTGGATGTTTACCTTTATCACATCAAAAGAAATATTGTTAGAAAGGTGTTTAATGTTTTGCAGATGGATAGATTACTGTTATTAGTTCTCATTTCATTGTTAATTTTTAAAACCATAAGGTTGGAAGTATCAATATGCCTTTCAATATACCTTAGTGGAATTTATTAAATTTTCATGGATGTCCTTTAGGGGGTTCAGGAAGTTATTTCTATTGCTAGATTTCTGGAAGATTTATCAGGAATGAGTGTCAGACATTGTCAGACGTCCATTGAAATCATCATGGTCTTTTCCTTTATTCTATTAATATGATGTATTACACTGATTGATTTTTAAATTTGTATTGGTAGGATAATTCCACTTGGTTATATTGTCTAACTTTTTTCTAATTTTCTTTCATTTTTATTACAGATGAGGCCTCACTCTGTCACCCAGGTTGGGGTGGAGTGGCACAGTCACAGCTCACTATAACCTCAAGCTCCTGGGCTCAAGTGATCCTGCCACCTCAGCCTCCTAAGTAGCTGGAACTACAGATGTGCACTGCCATGCCAGGCTTGTCTAACATTTTTATGTGTTGCTTCATCCAGTTTGCTAGAGTTTTTGGAGATTTCTGTCTTCATTCATGAGGGATAATAGTCTGCACTTTTATTTTCTTGTGATACTTTTGTCTGATTTGTTATCTGGGTAATACTGGCCTTGAAAATGAATTGATGTTTTCCTGCTTCTCTGCTTTGCAAGTGTTTGTGAAGGATTGGTTATTCATTAAGTGTTTAATAGAATTCACTAGTGAAGCTATGTGAGCCAGGGCTAGACTGATGAAGAGTTTTCATTAGTCTAATCTGTTTACTTGCTGTATAAGTACGCATATATTCTCTTTCTTCTTGATTTAATTTTACACTTTGTGTATAGCAGGGAATCTGTGTCTAATTTGTAGTATTTCATGCTTCTAGGTTTTCATGGCAGTTGAGATGTAAGAATAACAATAATGTTGGGAGAAGGAAGTTGTGGACAATCCATGAATATCCCAACATCTGTTGTAGGAAGGTTAAGATTACTTTTTTTTTTTTTGCTGTACTGAACTGAATACTCTTATTTATAATGTCAGACAAATGTAATGTTGTATATAAATAGAACTAGGAAAATGTGCCATTTGTCTTAGTATTTAATCAAGATGGAAGTCTGGGCCTACCTCCTCTCTTTTATTAATATGTAGACAGGACACCAACACAAATTAGAATGAAGACAAACAAAATGTTAGCAAATGAAGAATGGTATCAATTGGTTAAAATGTGATGAAATAGAGTGGTGAATATTTACATAGAATCCATGATGTGTTAGGTGCTATTTCAAGCTATTTGCACATATAGTTTTAATACCAATGACGTTAAAATGTATAACACAAAGATTCATATAAATAAAAATTACAACATTGTAAATAATATTAGGTGACACTAAAACTGTCATAGAAATACACATTTATATAAAACATAAAGTAACATGAAGTATTAAATTTTAGAAACTTTGATTACTAATCAGATGAACAACTGATTAGCCTTTTTATCCAGTAAAAAAGGCATACATATTATTTTCAAATTCCAGAGACAAATATTTTAAATATTGAAGTTGAAGACCTAAAAATGTGTCACTGACCTCATGGAAGTAGATATTCACTAGGTGATATTTTCTAGGCTCTCTGAAATTATATCAGAAAAATGTGAATTAGAATATAACCCATAAATAATATCTGGCCACATACAAAGTAATTGAAGATCAATTTAAATGGCTATTGGATTAAGAAATAGGGACTGAGGTAAATTTGCAGTGTCAGGGAGGATCTAAGGAGGAAGCATTGACACTGGAGCCCAAGGACCTGGGATCACAGAACAGATTCTACCAGTGCTAACTTACTGCTCCACAGAAAACATCAATTCTGCTCATGCGCAGGTACAATTCATCAAGAAAGGAATTACAACTTCAGAAATGTGTTCAAAATATATCCATACTTTGACATATTAATGAAGTAATCACATTCTACACATAACTACTCCATATGGAATACTGGGGAGGAGGTGTTCCAAATAAAGAGACTGAGGATTTCTCATGAGAACTCAGTGTCTGCTAGAAAATATCTAAGTAAAATATTTTACTTATGTGGAAAGTGTGGATGTTTGTGCATCAAAAGTTTCAAGAATCCCTAAAATTTACAATGGAGATGAGGAGAAAATATCAGAATTTCCCAGCACCAGAAATAAGGCAAGAAAAAATTCAGAGGGGTTGTAAATGTGAAAAGCCAATGGCTGGTCACACAGCAACATTGATAACCTTGTGCCTGGACAACTAGAATAAATACATAAACATACACATTGAAAATATTTCCAATATTAGATCTCCCTCATGTGAGAACTAAATTATAAAGATTGAAGCATAGAAGAAAATAAGCTACCAGAATAAATTTGATTACACATAAATTTCTGATATTGAAACTGTCACAAATGTTTAAGTTGGTAGTGGAAGACAAAGGACATATAATCTTGGGAGTCCTAAGGCCCTGCCCACTGCCAGTCCCTCCACACTACTACAGCTGATGCTTTCTGGAAATCACCACCTCCTGGCAGGAGCCCAACCAGCACAAATATAGAGCATTAAACCACCAAAGCTAAGGAGGCTCACAGAGTCTATTGCACCCTTCACCACCTCCACTGGAACAGGCGCTGGTATCCATGGCTCAGAGACCCAAAGATGGTTCACATCACAGGGCTCTATGCAGACAACCCCCAGTACCAGCCCAAAGCCACGTAGACCTGCTGGGTGGCTAGACCCAGAAGAGAGACAACAATCAATGCACTTTGGCTTACAGGAAGCCATGCCCATAGGAAAAAGGGGAGAGTACTACGTCAAGGGAACACCCCGTGGGATGAAAGAGTCTGAACAACAGTCTTCAGCCCTAGACCTTTCCTCTGACAGAGTCTACCAAAATGAGAAGGAACCAGAAAACCAACCCTGGTAATCTGACAAAACAAGAATCTTCAACACCCCCCAAAAAATCACACCAGTTCATCACCAATGGATCCAAACAAAGAAGAAATCACTGATTCATCTAAAAAAAAATTCAGGTTAGTTATTAAGCTAATCAGGGAGGGGCCAGAGAAAGATGAAGCCCAATGCAAGAAAATCCAAAAAATGATACAATACGTGAAGGGAGAATTATTCAAGGAAATAGATAGCTTAAATAAAAAAATAAAAAATCAGGAAACTTTGGACGTACTTTTAGAAATGTGAAATGCTCTGGAAAGTCTCAGCAATAGAATTGAACAAGTAGAAGAAAGAAATTCAGAATTCGAAGACAAGGTCTTTGATTTAACCCAATCCAATAAAGACAAAGAAAAAAGAATAAGAAAATATGAGCAAAGTCTCCAAGGAGTCTGGCATTCTGTTAAATGATGAAACCTAACACTAATTGGTGTACCTGAGGAAGAAGTGAATTCTAAAAGCCAGGAAAACATATTTGGGAGAATAATCTAGGAAAACTTCCATGGCCTTGTGAGAGACCTAGACATCCAAATACAAGAACCACAAATAACACCTGGGAAATTCATCACAAAAAGATCTTAGCCTAGGCACATTGTCATTAGGTTATCCAAAGTTAAGACAAAGGAAAGAATCTTAAGAGCTGTGAGACAGAAGCACTAGGTAACCTATAAAGGAAAACCTGTCAAATTAACAGCAGATTTCACAGCAGGAACCTTACAAGCTAGATGGGATTGGGGCCCTTTCTTCAGCCTCCTCAAACAAAACAATTATCAGCCAAGAATTTTGTATCCAGCAAAACTAAACATCATATATGAAGGAAAGATACAGTCATTTTCAGACAAACAAATGCTGACAGAATTTGCCATTACCAAGCCAGGACTCTAAGAACTGCTAAAAGGAGCTCTAAATCATGAAACAAATCCTGGAAACACATCAAAACAGAACTTCATTAACGCATAAATCACACAGGACCTATAAAACAAAAATACAAGTTAAAAAACAAAAACAAAGTACAGAGGCAACAAAGAGCATGATGAAAGCAATGGTACCTCACTTTTTAATACTAATGTTGGTTGTAAATGGCTTAAATGCTCCACTTACAAGATACAGAACCACAGAATGGATAACAACTCACCAACTAACTATCTGCTGCCTTCAGGAGACTCACCTAACACATAACGACTTACATAAACTTAAGGAAAGTGGTAGAAAAAGGCATTTCATGCAAATGGACACCAAAAGCAAGCAGCAGTAACTATTCTCATATGAGACAAAACAAACTTTAAAGCAACAGTAGCTAAAAGAGACAAAGAGAGACAGTATATCATCTGTCACCTGACAGTCTCATCCAACAGAAAAATATGACAATCCTAAACATATGTGAACCTAACACTGGAGCTCCCAAATTTATAAAACAATTACTAGTAGACATAAGAAATAAGATAGACAGCAACACAATAATAGTGGGGGACTTCAATACTCCACTGACAGCACTAGACAGGTCATCAAGACAGAAAGTCAACAAAGAAACAATGGATTTAAACTATACTTTGGAACAAATGGACTTAACAGATATATATAGAACATTTCATCCAACAACCACAGAATACACATTCTATTCAACAGCACATGGAATTTTCTCCAAGATAGACCATATGATAGGCCATAAAATGAGTCTCAATAAATTTAAGAAAATTGAAATTGTATCACGCACTCTCTCACATCACAATGGAATAAAACTGAAAATCAACTCCAAAAGGAATCTTCGAAACCATGCAAATACATGGAAATTAAATAACCTGCTCCTGAATGAGCATTGGGTGAAAAACGAAATCAAGATGGAAATGTAAAAAATTTCTTCGAACTGGATGACACAACCTATCAAGACCTCTGGGATACAGCAAAGGCAGTGCTAAGAGGAAAGTTTATAGCACTAAACACCTACGTCGAAAAGTCTGAAAGAGCACAGACAATCTAAGTTCACATCTCAGGGAACTAGAGAAGGAGGAACAAGCCAAACCCAATCCCAGCAAACAAAGGAAATAACCAAGATCAGAGCAGAACTAAATGAAATTGACACAACAACAACAACAACAAAAATACAAAACATAAATAAAACAAAAATTTGGTTATTTGAAAAGATA' 

def findStopCodon(dnaStr, startIndex, stopCodon): 
    currIndex = dnaStr.index(stopCodon, startIndex+3) 
    while (currIndex != -1): 
     diff = currIndex - startIndex 
     if (diff % 3 == 0): 
      return currIndex 
     else: 
      currIndex = dnaStr.index(stopCodon, currIndex+1) 
    return -1 

def findGene(dna, where): 
    startIndex = dna.index('ATG', where) 
    if startIndex == -1: 
     return '' 
    taa_index = findStopCodon(dna, startIndex, 'TAA') 
    tag_index = findStopCodon(dna, startIndex, 'TAG') 
    tga_index = findStopCodon(dna, startIndex, 'TGA') 
    minIndex = 0 
    if (taa_index == -1 | (tga_index != -1 & tga_index < taa_index)): 
     minIndex = tga_index 
    else: 
     minIndex = taa_index 
    if (minIndex == -1 | (tag_index != -1 & tag_index < minIndex)): 
     minIndex = tag_index 
    if minIndex == -1: 
     return "" 
    return dna[startIndex:minIndex + 3] 

def printAllGenes(dna): 
    startIndex = 0 

    while True: 
     currentGene = findGene(dna, startIndex) 
     if len(currentGene) == 0: 
      break 

     print(currentGene) 
     startIndex = dna.index(currentGene, startIndex) + len(currentGene) 

printAllGenes(gene_sequence) 

它輸出29個基因，我不知道還有多少可以找到。下面一行中的錯誤導致它在通過鏈的其餘部分之前結束。

currIndex = dnaStr.index(stopCodon, currIndex+1) 

Answer 1

你似乎是一個不正確的印象是.index()返回-1上未能找到字符串：

currIndex = dnaStr.index(stopCodon, startIndex+3) 
while (currIndex != -1): 

這是不是這樣的，它拋出，而不是一個錯誤：

>>> help(str.index) 
Help on method_descriptor: 

index(...) 
    S.index(sub[, start[, end]]) -> int 

    Like S.find() but raise ValueError when the substring is not found. 

>>> 

正如幫助解釋說明，您確實需要.find()方法。

讓我們嘗試只是你的代碼，而不是僅僅打補丁：

gene_sequence = 'AAC...ATA' # supply your original sequence here 

STOP_CODONS = {'TAA', 'TAG', 'TGA'} 

def findStopCodon(dnaStr, startIndex, stopCodons): 

    for currIndex in range(startIndex + 3, len(dnaStr), 3): 
     if dnaStr[currIndex:currIndex + 3] in stopCodons: 
      return currIndex 

    return -1 

def findGene(dna, where): 
    startIndex = dna.find('ATG', where) 

    if startIndex == -1: 
     return '', startIndex 

    stopIndex = findStopCodon(dna, startIndex, STOP_CODONS) 

    if stopIndex == -1: 
     return '', stopIndex 

    return dna[startIndex:stopIndex + 3], stopIndex + 3 

def printAllGenes(dna): 
    startIndex = 0 

    while True: 
     currentGene, startIndex = findGene(dna, startIndex) 

     if not currentGene: # empty strings are False 
      break 

     print(currentGene) 

printAllGenes(gene_sequence) 

此輸出69個基因和不破。測試它以確保它確實做到了你想要的。