Unbalanced parenthesis python

Question

I have the following code:

def commandType(self):
    import re
    print self.cmds[self.counter]
    if re.match("@",self.cmds[self.counter]):
        return Parser.A_COMMAND

    elif re.match('(',self.cmds[self.counter]):
        return Parser.L_COMMAND

    else:
        return Parser.C_COMMAND

and on this line: elif re.match('(',self.cmds[self.counter]):

I'm getting an error.

What am I doing wrong?

Answer 1

Parentheses have special meaning in regular expressions. You can escape the paren but you really do not need a regex at all for this problem:

def commandType(self):
    print self.cmds[self.counter]
    if '@' in self.cmds[self.counter]):
        return Parser.A_COMMAND

    elif '(' in self.cmds[self.counter]:
        return Parser.L_COMMAND

    else:
        return Parser.C_COMMAND

Answer 2

The parenthesis '(' and ')' are used as grouping mechanism and scope operators in regexps. You have to escape them (and any other control symbols) via backslash, e.g. '\('.