Python：使用re.sub多次替换多个子字符串

Question

I am trying to correct a text that has some very typical scanning errors (l mistaken for I and vice-versa). Basically I would like to have the replacement string in re.sub to depend on the number of times the 'I' is detected, something like that:

re.sub("(\\w+)(I+)(\\w*)", "\\g<1>l+\\g<3>", "I am stiII here.")

What's the best way to achieve this?

Answer 1

Pass a function as the replacement string, as described in the docs . Your function can identify the mistake and create the best substitution based on that.

def replacement(match):
    if "I" in match.group(2):
        return match.group(1) + "l" * len(match.group(2)) + match.group(3)
    # Add additional cases here and as ORs in your regex

re.sub(r"(\w+)(II+)(\w*)", replacement, "I am stiII here.")
>>> I am still here.

(note that I modified your regex so the repeated Is would appear in one group.)

Answer 2

你可以使用一个环视来替换I后面或之前的另一个I ：

print re.sub("(?<=I)I|I(?=I)", "l", "I am stiII here.")

Answer 3

It seems to me that you could do something like:

def replace_L(match):
    return match.group(0).replace(match.group(1),'l'*len(match.group(1)))

string_I_want=re.sub(r'\w+(I+)\w*',replace_L,'I am stiII here.')

Answer 4

based on the answer proposed by DNS, I built something a bit more complicated to catch all the cases (or at least most of them), trying not to add too many errors:

def Irepl(matchobj):
    # Catch acronyms
    if matchobj.group(0).isupper():
        return matchobj.group(0)
    else:
        # Replace Group2 with 'l's
        return matchobj.group(1) + 'l'*len(matchobj.group(2)) + matchobj.group(3)


# Impossible to know if first letter is correct or not (possibly a name)
I_FOR_l_PATTERN = "([a-zA-HJ-Z]+?)(I+)(\w*)"
for line in lines:
    tmp_line = line.replace("l'", "I'").replace("'I", "'l").replace(" l ", " I ")
    tmp_line = re.sub("^l ", "I ", tmp_line)

    cor_line = re.sub(I_FOR_l_PATTERN, Irepl, tmp_line)

    # Loop to catch all errors in a word (iIIegaI for example)
    while cor_line != tmp_line:
        tmp_line = cor_line
        cor_line = re.sub(I_FOR_l_PATTERN, Irepl, tmp_line)

Hope this helps somebody else!