替换位于其间的字符串

Question

Here is my problem: in a variable that is text and contains commas, I try to delete only the commas located between two strings (in fact [ and ] ). For example using the following string:

input =  "The sun shines, that's fine [not, for, everyone] and if it rains, it Will Be better."
output = "The sun shines, that's fine [not for everyone] and if it rains, it Will Be better."

I know how to use .replace for the whole variable, but I can not do it for a part of it. There are some topics approaching on this site, but I did not manage to exploit them for my own question, eg:

• Repeatedly extract a line between two delimiters in a text file, Python
• Python finding substring between certain characters using regex and replace()
• replace string between two quotes

Answer 1

import re
Variable = "The sun shines, that's fine [not, for, everyone] and if it rains, it Will Be better."
Variable1 = re.sub("\[[^]]*\]", lambda x:x.group(0).replace(',',''), Variable)

First you need to find the parts of the string that need to be rewritten (you do this with re.sub ). Then you rewrite that parts.

The function var1 = re.sub("re", fun, var) means: find all substrings in te variable var that conform to "re" ; process them with the function fun ; return the result; the result will be saved to the var1 variable.

The regular expression "[[^]]*]" means: find substrings that start with [ ( \\[ in re), contain everything except ] ( [^]]* in re) and end with ] ( \\] in re).

For every found occurrence run a function that convert this occurrence to something new. The function is:

lambda x: group(0).replace(',', '')

That means: take the string that found ( group(0) ), replace ',' with '' (remove , in other words) and return the result.

Answer 2

You can use an expression like this to match them (if the brackets are balanced):

,(?=[^][]*\])

Used something like:

re.sub(r",(?=[^][]*\])", "", str)

Answer 3

Here is a non-regex method. You can replace your [] delimiters with say [/ and /] , and then split on the / delimiter. Then every odd string in the split list needs to be processed for comma removal, which can be done while rebuilding the string in a list comprehension:

>>> Variable = "The sun shines, that's fine [not, for, everyone] and if it rains,
                it Will Be better."
>>> chunks = Variable.replace('[','[/').replace(']','/]').split('/')
>>> ''.join(sen.replace(',','') if i%2 else sen for i, sen in enumerate(chunks))
"The sun shines, that's fine [not for everyone] and if it rains, it Will Be 
 better."

Answer 4

If you don't fancy learning regular expressions (see other responses on this page), you can use the partition command.

sentence = "the quick, brown [fox, jumped , over] the lazy dog"
left, bracket, rest = sentence.partition("[")
block, bracket, right = rest.partition("]")

"block" is now the part of the string in between the brackets, "left" is what was to the left of the opening bracket and "right" is what was to the right of the opening bracket.

You can then recover the full sentence with:

new_sentence = left + "[" + block.replace(",","") + "]" + right
print new_sentence # the quick, brown [fox jumped over] the lazy dog

If you have more than one block, you can put this all in a for loop, applying the partition command to "right" at every step.

Or you could learn regular expressions! It will be worth it in the long run.