def get_length(dna):

    """ (str) -> int

    Return the length of the DNA sequence dna.

    >>> get_length('ATCGAT')
    6
    >>> get_length('ATCG')
    4
    """
    return len(dna)

字元長度比較返回邏輯值

def is_longer(dna1, dna2):
    """ (str, str) -> bool

    Return True if and only if DNA sequence dna1 is longer than DNA sequence
    dna2.

    >>> is_longer('ATCG', 'AT')
    True
    >>> is_longer('ATCG', 'ATCGGA')
    False
    """
    if len(dna1) > len(dna2):
        return True
    else:
        return False
 

相同字元個數

def count_nucleotides(dna, nucleotide):
    """ (str, str) -> int

    Return the number of occurrences of nucleotide in the DNA sequence dna.

    >>> count_nucleotides('ATCGGC', 'G')
    2
    >>> count_nucleotides('ATCTA', 'G')
    0
    """
    return dna.count(nucleotide)
 

字元相同返回邏輯值

def contains_sequence(dna1, dna2):
    """ (str, str) -> bool

    Return True if and only if DNA sequence dna2 occurs in the DNA sequence
    dna1.

    >>> contains_sequence('ATCGGC', 'GG')
    True
    >>> contains_sequence('ATCGGC', 'GT')
    False

    """
    if dna2 in dna1:
        return True
    else:
        return False
 

判斷是否包含某字元

def is_valid_sequence(nucleotide):
    """ (str) -> bool

    Return True if and only if the DNA sequence is valid.
    >>> is_valid_sequence('A')
    True
    >>> is_valid_sequence('T')
    True
    >>>is_valid_sequence('C')
    True
    >>>is_valid_sequence('G')
    True
    >>>is_valid_sequence('D')
    False
    >>>is_valid_sequence('B')
    False
     """
    str='ATCG'
    if str.find(nucleotide)==-1:
        return False
    else:
        return True

插入字元

def insert_sequence(dna1,dna2,location):
    """ (str, str, int) -> str
    return the dna sequence obtained bu inserting dna2 into dna1 at the location.
    >>>insert_sequence('CCGG','AT',2)
    'CCATGG'
    >>>insert_sequence('AT','G',1)
    'AGT'
    """
    return dna1[:location] + dna2 + dna1[location:]

輸出對映字元

def get_complement(nucleotide):
    """ (str) -> str
    return the nucleotide's complement
    >>>get_complement('A')
    'T'
    >>>get_complement('C')
    'G'
    """
    in_str= 'ATCG'
    out_str= 'TAGC'
    map_table=str.maketrans(in_str,out_str)
    return nucleotide.translate(map_table)

字元逆序排列

def get_complementary_sequence(dna):
    """ (str) -> str
    return the complementary dna sequence
    >>>get_complementary_sequence('AT')
    'TA'
    >>>get_complementary_sequence('CG')
  'GC'
    """
    return dna[::-1]