removeSqlComments

def removeSqlComments(source):
    result = []

    state = 0
    # states:
    # 0 - initial state
    # 1 - have single '-'
    # 2 - have double '-' (valid comment)
    # 3 - have single "'"
    # 4 - have single '\' inside quotes
    for char in source:
        result.append(char)
        if state == 0:
            if char == '-':
                state = 1
            elif char == "'":
                state = 3
            else:
                state = 0
        elif state == 1:
            if char == '-':
                state = 2
                result.pop()
                result.pop()
            else:
                state = 0
        elif state == 2:
            if char == '\n':
                state = 0
            else:
                result.pop()
                state = 2
        elif state == 3:
            if char == '\\':
                state = 4
            elif char == "'":
                state = 0
            else:
                state = 3
        elif state == 4:
            state = 3

    print ''.join(result)

test1 = r"""
SELECT * FROM Students -- here's comment1
WHERE age > 20 and name like 'A%\\'--start of a comment'; -- also comment
"""

removeSqlComments(test1)