CODEWITHSUNDEEP
pythonstring-parsing
MxLDevs
MxLDevs

Reputation: 19506

Splitting on spaces, except between certain characters

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?

Upvotes: 6

Views: 7362

Answers (5)

ryonthli
ryonthli

Reputation: 1

Here's another non-regex solution to split a string between spaces except when a sub-string is between parenthesis.

    file_line = 'type("book") title("golden apples") pages(10 - 35 70 200 - 234) comments("good read")'
    list_of_params = []
    param = ''

    between_parenthesis = False
    for character in file_line:
        if between_parenthesis:
            if character == ')':
                between_parenthesis= False
        else:
            if character == '(':
                between_parenthesis= True

            if character == ' ':
                list_of_params.append(param)
                param = ''
                continue

        param += character

    list_of_params.append(param)
    print(list_of_params)

result:

    ['type("book")', 'title("golden apples")', 'pages(10 - 35 70 200 - 234)', 'comments("good read")']

Upvotes: 0

MarcinKonowalczyk
MarcinKonowalczyk

Reputation: 2788

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.

Upvotes: 1

Karl Knechtel
Karl Knechtel

Reputation: 61498

Split on ") " and add a ) back to each element except the last.

Upvotes: 3

yas
yas

Reputation: 3620

I would try using a positive look-behind assertion. 

r'(?<=\))\s+'

Example:

>>> 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")']

Upvotes: 1

Narendra Yadala
Narendra Yadala

Reputation: 9664

This regex should work for you \s+(?=[^()]*(?:\(|$))

result = re.split(r"\s+(?=[^()]*(?:\(|$))", subject)

Explanation

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)
   )
)
"""

Upvotes: 16

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