Budget.txt

+  3000 Salary
-   100 Expense
-   200 Expense
-    50 Expense

=       Group
-   100 Expense
-   200 Expense
-    50 Expense

fabfile.py

def budget():
	output['status'] = False
	groups = []
	group = None
	with open('Budget.txt') as handler:
		for line in handler:
			if line[0] in '=+' and group is None:
				value = line[1:8].strip()
				value = int(value) if len(value) else 0
				label = line[8:]
				group = [[line[0], value, label]]
			elif re.search('^[-+]', line):
				op = line[0]
				value = line[1:8].strip()
				value = int(value) if len(value) else 0
				label = line[8:]
				group.append([op, value, label])
			elif re.match('^\s*$', line) and group is not None:
				groups.append(group)
				group = None
		if group is not None and groups[-1] != group:
			groups.append(group)
	for group in groups:
		if group[0][0] == '=':
			value = 0
			for op in group[1:]:
				value += op[1]
		elif group[0][0] == '+':
			value = group[0][1]
			for op in group[1:]:
				if op[0] == '+':
					value += op[1]
				elif op[0] == '-':
					value -= op[1]
		group[1:] = sorted(group[1:], key=lambda l: l[1])
		if group[0][0] == '=':
			group[0][1] = value
		else:
			group.append(['=', value, '\n'])
	updated = ['\n']
	for group in groups:
		for op in group:
			updated.append('%s %5d %s' % tuple(op))
		updated.append('\n')
	with open('Budget.txt', 'w') as handler:
		for line in updated:
			handler.write(line)