I am parsing a file that has lines such as
type("book") title("golden apples") pages(10-35 70 200-234) comments("good read")
And I want to split this into separate fields.
In my example, there are four fields: type, title, pages, and comments.
The desired result after splitting is
['type("book")', 'title("golden apples")', 'pages(10-35 70 200-234)', 'comments("good read")]
It is evident that a simple string split won't work, because it will just split at every space. I want to split on spaces, but preserve anything in between parenthesis and quotation marks.
How can I split this?
preguntado el 10 de marzo de 12 a las 07:03
Esta expresión regular debería funcionar para ti
result = re.split(r"\s+(?=[^()]*(?:\(|$))", subject)
r""" \s # Match a single character that is a “whitespace character” (spaces, tabs, and line breaks) + # Between one and unlimited times, as many times as possible, giving back as needed (greedy) (?= # Assert that the regex below can be matched, starting at this position (positive lookahead) [^()] # Match a single character NOT present in the list “()” * # Between zero and unlimited times, as many times as possible, giving back as needed (greedy) (?: # Match the regular expression below # Match either the regular expression below (attempting the next alternative only if this one fails) \( # Match the character “(” literally | # Or match regular expression number 2 below (the entire group fails if this one fails to match) $ # Assert position at the end of a line (at the end of the string or before a line break character) ) ) """
") " y agrega un
) back to each element except the last.
I would try using a positive look-behind assertion.
>>> import re >>> result = re.split(r'(?<=\))\s+', 'type("book") title("golden apples") pages(10-35 70 200-234) comments("good read")') >>> result ['type("book")', 'title("golden apples")', 'pages(10-35 70 200-234)', 'comments( "good read")']
Let me add a non-regex solution:
line = 'type("book") title("golden apples") pages(10-35 70 200-234) comments("good read")' count = 0 # Bracket counter last_break = 0 # Index of the last break parts =  for j,char in enumerate(line): if char is '(': count += 1 elif char is ')': count -= 1 elif char is ' ' and count is 0: parts.append(line[last_break:(j)]) last_break = j+1 parts.append(line[last_break:]) # Add last element parts = tuple(p for p in parts if p) # Convert to tuple and remove empty for p in parts: print(p)
In general there are certain things you cannot do with regular expressions, and there can be serious performance penalties (especially for lookahead and lookbehind) which can cause them not to be the best solution for a certain problem.
Also; I thought I'd mention the
pyparsing module which can be used to create custom text parsers.