3 = 123+4+5-6*7^89

First verifiable instance of error?

Did a little fishing for overflow candidates with the following regex:

  [1-9]{3,}\^[1-9]{3,}

...caught 58 results between 266 and 10940:

  266 = 123^456-78-9
  ...
  10940 = 12345^6789

My kung fu isn't Python so I don't know how types are handled. That eval() function sure smells suicidal for anything remotely serious though.