Python on appengine: error with eval()

Question

I'm using App Engine's webapp. This request handler outputs a form with a text field. On submission, it will get the text and add <h1> tags to lines that start with #. I used repr() to be able to split the text into a list of lines, and eval() to analyze the text from each line without the u' at the start of the string that comes from repr().

class Test(webapp.RequestHandler):
    def get(self):
        self.response.out.write('<form method=\'post\' action=\'\'>')
        self.response.out.write('<textarea name=\'text\'></textarea>')
        self.response.out.write('<input type=\'submit\' value=\'Submit\'/>')
        self.response.out.write('</form>')
    def post(self):
        output = []
        for line in repr(self.request.get('text')).split('\\n'):
            if eval(line)[0] == '#':
                output.append('<h1>'+line+'</h1>')
            else:
                output.append(line)
        self.response.out.write('\\n'.join(output))

The way the code is now, its giving me this error:

File "<string>", line 1
    u'#somestring\r
                  ^
SyntaxError: EOL while scanning string literal

If I use just line[0] instead of eval(line)[0], everything works fine except that it doesn't work for the first line. Even if the first line starts with #, the conditional will go for the else because the first characters will be u' and not #. Trying to work around that with eval() is giving me that error. How can I work around this problem?

Answer 1

To split the text, the strings have a built in splitlines method:

for line in self.request.get('text').splitlines():
    ... do whatever ...

Then to see if a particular line begins with a #, try this:

if line.strip()[0]=='#':
    ... do whatever ...

Put together:

for line in self.request.get('text').splitlines():
    if line.strip()[0] == '#':
        ... do whatever ...