[人工智能]使用pysam读取DNA序列

先创建一个读对象：

fasta_open = pysam.Fastafile(fasta_file)

读出来的DNA序列是字符串的格式：

seq_dna = fasta_open.fetch('chr1', 0, 100)
# output:'NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN'

将序列转为one-hot编码：

'''
A: [1, 0, 0, 0]
C: [0, 1, 0, 0]
G: [0, 0, 1, 0]
T: [0, 0, 0, 1]
'''

seq_1hot = dna_1hot(seq_dna, n_uniform=False, n_sample=False).astype('float32')

'''
output: 
array([[1., 0., 0., 0.],
       [1., 0., 0., 0.],
       [1., 0., 0., 0.],
       [0., 0., 0., 1.],
       [0., 1., 0., 0.],
       [0., 0., 1., 0.]], dtype=float32)
'''

def dna_1hot(seq, seq_len=None, n_uniform=False, n_sample=False):
  """ dna_1hot

    Args:
      seq:       nucleotide sequence.
      seq_len:   length to extend/trim sequences to.
      n_uniform: represent N's as 0.25, forcing float16,
      n_sample:  sample ACGT for N

    Returns:
      seq_code: length by nucleotides array representation.
    """
  if seq_len is None:
    seq_len = len(seq)
    seq_start = 0
  else:
    if seq_len <= len(seq):
      # trim the sequence
      seq_trim = (len(seq) - seq_len) // 2
      seq = seq[seq_trim:seq_trim + seq_len]
      seq_start = 0
    else:
      seq_start = (seq_len - len(seq)) // 2

  seq = seq.upper()

  # map nt's to a matrix len(seq)x4 of 0's and 1's.
  if n_uniform:
    seq_code = np.zeros((seq_len, 4), dtype='float16')
  else:
    seq_code = np.zeros((seq_len, 4), dtype='bool')
    
  for i in range(seq_len):
    if i >= seq_start and i - seq_start < len(seq):
      nt = seq[i - seq_start]
      if nt == 'A':
        seq_code[i, 0] = 1
      elif nt == 'C':
        seq_code[i, 1] = 1
      elif nt == 'G':
        seq_code[i, 2] = 1
      elif nt == 'T':
        seq_code[i, 3] = 1
      else:
        if n_uniform:
          seq_code[i, :] = 0.25
        elif n_sample:
          ni = random.randint(0,3)
          seq_code[i, ni] = 1

  return seq_code