python 中获取反向序列及互补序列

001、获取反向序列

>>> myseq = 'AGCTGGCTA'
>>> myseq[::-1]                                          ## 利用切片实现
'ATCGGTCGA'
>>> temp = []
>>> for i in reversed(myseq):                            ## 借助reversed函数实现
...     temp.append(i)
...
>>> temp
['A', 'T', 'C', 'G', 'G', 'T', 'C', 'G', 'A']
>>> "".join(temp)             
'ATCGGTCGA'

002、获取互补序列

>>> myseq = 'AGCTGGCTA'                                  ## 测试字符串
>>> myseq = myseq.replace("A", "t")                      ## 防止碱基混淆，先转换为互补碱基的小写字母
>>> myseq = myseq.replace("T", "a")
>>> myseq = myseq.replace("C", "g")
>>> myseq = myseq.replace("G", "c")
>>> myseq
'tcgaccgat'
>>> myseq = myseq.upper()                                ## 整个字符串转换为大小
>>> myseq
'TCGACCGAT'

003、获取反向互补序列

方法1、

>>> myseq = 'AGCTGGCTA'
>>> str1 = ""
>>> for i in myseq:                                     ## 利用循环获取互补序列
...     if i == "A":
...             str1 += "T"
...     if i == "T":
...             str1 += "A"
...     if i == "C":
...             str1 += "G"
...     if i == "G":
...             str1 += "C"
...
>>> str1         
'TCGACCGAT'
>>> str1[::-1]                                         ## 获取反向序列
'TAGCCAGCT'

方法2：

>>> myseq = 'AGCTGGCTA'
>>> dict1 = {"A":"T", "T":"A", "C":"G", "G":"C"}     ## 匹配模板
>>> [dict1[k] for k in myseq]                        ## 利用列表内循环结构获取互补序列
['T', 'C', 'G', 'A', 'C', 'C', 'G', 'A', 'T']
>>> [dict1[k] for k in myseq][::-1]
['T', 'A', 'G', 'C', 'C', 'A', 'G', 'C', 'T']
>>> "".join([dict1[k] for k in myseq][::-1])         ## 取反并转换为字符串
'TAGCCAGCT'

参考：https://mp.weixin.qq.com/s?__biz=MzkyMTI1MTYxNA==&mid=2247493739&idx=1&sn=f690c93761307e6ec9bb77cca2eb4619&chksm=c184d21af6f35b0cda1d964ed896adee1091e1f615b7f6be0caf2508105275ca3ae66889c58e&mpshare=1&scene=23&srcid=0811LY0ghlyV0yNXki8WcW6m&sharer_sharetime=1660215059305&sharer_shareid=50b75c6a886e09824b582fb782a7678b#rd