[英]In Python, what is the fastest way to replace certain characters in a given string other than using str.translate()?
What is the fastest way to replace certain characters in a given string other than using str.translate()
?除了使用
str.translate()
之外,替换给定字符串中某些字符的最快方法是什么?
Given a sequence
that only consists of letters "A", "T", "G", and "C", I want to replace each instance of "A" with "T", "T" with "A", "C" with "G", and "G" with "C".给定一个仅由字母“A”、“T”、“G”和“C”组成的
sequence
,我想用“T”替换“A”的每个实例,用“A”、“C”替换“T” ”与“G”,“G”与“C”。 To do this, I used an ascii dictionary map = {65:84,84:65,71:67,67:71}
, and do sequence.translate(map)
.为此,我使用了 ascii 字典
map = {65:84,84:65,71:67,67:71}
,并执行sequence.translate(map)
。 However, in Python 3.8
this appears to be slow.但是,在
Python 3.8
中,这似乎很慢。 I saw people mention using byte
or bytearray
to do this, but I just don't know how to make it work.我看到有人提到使用
byte
或bytearray
来做到这一点,但我只是不知道如何让它工作。
It looks like I first need to encode the sequence using sequence.encode('ascii', 'ignore')
and then use translate()
to do the translation?看起来我首先需要使用
sequence.encode('ascii', 'ignore')
对序列进行编码,然后使用translate()
进行翻译?
Can anybody please help me?有人可以帮我吗?
For example,例如,
sequence = 'ATGCGTGCGCGACTTT'
# {'A':'T', 'T':'A', 'C':'G', 'G':'C'}
map_dict = {65:84,84:65,71:67,67:71}
# expect 'TACGCACGCGCTGAAA'
sequence.translate(map_dict)
Assumption here is the sequence is very long, then this should be O(1):假设这里的序列很长,那么这应该是 O(1):
If you maintain an index which contains the position of each letter in the sequence, then you just need to update the index to do bulk replacements.如果您维护一个包含序列中每个字母位置的索引,那么您只需要更新索引即可进行批量替换。
For example given seq = "AGCTTCGA"例如给定 seq = "AGCTTCGA"
index = {"A": {0, 7}, "G": {1, 6}, "C": {2, 5}, "T": {3, 4}}
and if I understand correctly you want to do a swap:如果我理解正确,您想进行交换:
def swap(index, charA, charB):
tmp = index[charB]
index[charB] = index[charA]
index[charA] = tmp
swap(index, "A", "T")
print(index)
# {'A': {3, 4}, 'G': {1, 6}, 'C': {2, 5}, 'T': {0, 7}}
I am going to assume that you want to just replace any occurrence of a string with another.我将假设您只想用另一个字符串替换任何出现的字符串。 Replace will not work in this case thank you for pointing this out but use:
在这种情况下,替换将不起作用感谢您指出这一点,但请使用:
for i in string:
match i:
case "A": i="T"
case "T": i="A"
case "C": i="G"
case "G": i="C"
continue
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