split a string at a certain index

Question

If I have a string and I want to split it at '.' which is not contained within brackets, how would I do it.

'(1.2).(2.1)' to get ['(1.2)', '(2.1)']

'(1.2).2' to get ['(1.2)', '2']

'1.(1.2)' to get ['1', '(1.2)']

Answer 1

This doesn't answer the general problem, but works for your examples:

>>> import re
>>> re.split(r'(?<=\))\.', '(1.2).(2.1)')
['(1.2)', '(2.1)']
>>> re.split(r'(?<=\))\.', '(1.2).2')
['(1.2)', '2']

This splits the string on any period after a closing parenthesis.

Answer 2

This program assumes that the input will be valid always, though it is fairly easy to include conditions to handle it properly.

def custom_split(data):
    element, opened, result = "", 0, []
    for char in data:
        # Immediately following if..elif can be shortened like this
        # opened += (char == ")") - (char == "(")
        # Wrote like that for readability

        if char == ")":
            opened -= 1
        elif char == "(":
            opened += 1

        if char == "." and opened == 0 and element != "":
            result.append(element)
            element = ""
        else:
            element += char

    if element != "":
        result.append(element)
    return result

print custom_split('(1.2).(2.1)')
print custom_split('(1.2).2')
print custom_split('2.2')
print custom_split('(2.2)')
print custom_split('2')

Output

['(1.2)', '(2.1)']
['(1.2)', '2']
['2', '2']
['(2.2)']
['2']

Answer 3

Using re seems to be the solution:

>>> import re
>>> r = re.compile(r'(?:[^.(]|\([^)]*\))+')
>>> r.findall('(1.2).(2.1)')
['(1.2)', '(2.1)']
>>> r.findall('(1.2).2')
['(1.2)', '2']
>>> r.findall('1.(1.2)')
['1', '(1.2)']

Answer 4

def split(s, level=0, result=''):
    if s == '':
        if result:
            return [result]
        else:
            return []
    if s.startswith('.') and level == 0:
        return [result] + split(s[1:], 0, '')
    level += s.startswith('(')
    level -= s.startswith(')')
    return split(s[1:], level, result + s[0])

Usage:

>>> split('(1.2).(2.1)')
['(1.2)', '(2.1)']
>>> split('(1.2).2')
['(1.2)', '2']
>>> split('1.(1.2)')
['1', '(1.2)']