Python练习

(1)生成随机序列

(2)反向互补序列

(3)查找序列

(1)生成随机序列

#########生成随机序列#############

def RandomSeq(SeqLength):

  #import random

  #import

  myT = ""

  myRT = list(range(0,int(SeqLength)))

  i = -1

  while len(myT) < SeqLength:

    b = random.choice('ACTG')

    myT = myT + b

    rb = ""

    if b == "A":

      rb = "T"

    elif b == "T":

      rb = "A"

    elif b == "C":

      rb = 'G'

    elif b == "G":

      rb = "C"

    myRT[i] = rb

    i = i-1

  myRT = "".join(myRT)

  return [myT,myRT]

################################

>>> RandomSeq(20)

['CGTCAGGCCTGTGAATCAGC', 'GCTGATTCACAGGCCTGACG']

>>>

################################

(2)反向互补序列

##############反向互补##################

def revCom(seq):

  seq = list(seq)

  myL = len(seq)

  #myRC = list(range(0,myL))

  End = -1

  myRC = ""

  while End >= 0-myL:

    b = seq[End]

    rb = ""

    if b == "A":

      rb = "T"

    elif b == "T":

      rb = "A"

    elif b == "C":

      rb = 'G'

    elif b == "G":

      rb = "C"

    End = End-1

    myRC = myRC+rb

  return myRC

################################

>>> revCom("CGTCAGGCCTGTGAATCAGC")

'GCTGATTCACAGGCCTGACG'

>>>

################################

(3)查找序列

#############找序列#############

[(m.start(0), m.end(0)) for m in re.finditer(pattern, string)]

在这里，pattern举例：

pattern = re.compile("ACGT[AT]GG")

string = "ACGTAGGAGCTGTCGATGCACGTTGGAAATGC"

################################

>>> string = "ACGTAGGAGCTGTCGATGCACGTTGGAAATGC"

>>> import re

>>> pattern = re.compile("ACGT[AT]GG")

>>> [(m.start(0), m.end(0)) for m in re.finditer(pattern, string)]

[(0, 7), (19, 26)]

>>>

################################