"[EMAIL PROTECTED]" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > Hi, > I have a string '((1,2), (3,4))' and I want to convert this into a > python tuple of numbers. But I do not want to use eval() because I do > not want to execute any code in that string and limit it to list of > numbers. > Is there any alternative way? > > Thanks. > Suresh >
Pyparsing comes with an example that parses strings representing lists. Here's that example, converted to parsing only tuples of numbers. Note that this does not presume that tuples are only pairs, but can be any number of numeric values, nested to any depth, and with arbitrary whitespace, etc. This grammar also includes converters by type, so that ints come out as ints, and floats as floats. (This grammar doesn't handle empty tuples, but it does handle tuples that include an extra ',' after the last tuple element.) -- Paul Download pyparsing at http://sourceforge.net/projects/pyparsing/ . from pyparsing import * integer = (Word(nums)|Word('-+',nums)).setName("integer") real = Combine(integer + "." + Optional(Word(nums))).setName("real") tupleStr = Forward().setName("tuple") tupleItem = real | integer | tupleStr tupleStr << ( Suppress("(") + delimitedList(tupleItem) + Optional(Suppress(",")) + Suppress(")") ) # add parse actions to do conversion during parsing integer.setParseAction( lambda toks: int(toks[0]) ) real.setParseAction( lambda toks: float(toks[0]) ) tupleStr.setParseAction( lambda toks: tuple(toks) ) s = '((1,2), (3,4), (-5,9.2),)' print tupleStr.parseString(s)[0] Gives: ((1, 2), (3, 4), (-5, 9.1999999999999993)) -- http://mail.python.org/mailman/listinfo/python-list
