URL encode GAE query string using Python

Question

I am programming a online Expression Calculator in GAE using Python. I am using query string to get the query and then evaluate the expression. For example for ishamsample.appspot.com/eval?q=9-6 browser should show {9-3}{6} This like query is working properly but the problem is + symbol. ishamsample.appspot.com/eval?q=1+6 Below is my code. I tried URL quoting

class Eval(webapp2.RequestHandler):
    def get(self):
        q=self.request.get('q')
        q=urllib.quote(q)
        code=eval(compile(q,'<string>', 'eval', __future__.division.compiler_flag))
        self.response.write('{'+q+'}{'+str(code)+'}')

For that browser shows output as {1%206}{1} enter image description here

How to overcome this issue.

Community · Accepted Answer · 2017-05-23 12:19:11Z

1

You should not encode the string you get as GET parameter on the server side. You should be decoding it; and GAE does that for you. Whoever is the client (here: you as a user) should encode the symbols before making an HTTP request.

Your request should look like:

http://.../?q=1%2B6

One comment that I cant resist making: EVAL IS EVIL. Please refer to a similar question. on how to do it using ast.literal_eval(..).

edited May 23, 2017 at 12:19

CommunityBot

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answered Nov 15, 2013 at 14:20

UltraInstinct

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Comments

Thomas · Accepted Answer · 2013-11-15 14:18:01Z

0

is a special symbol, it is supposed to replace spaces. In the url you should have %2B. If you post the query from a text input it should be encoded naturally. Nothing to do with python or GAE

answered Nov 15, 2013 at 14:18

Thomas

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2 Comments

Isham Mohamed Over a year ago

Nope in URL, users put + sign and thats why I need URL Encoding here. For example, if a user put ishamsample.appspot.com/eval?q=1+6 it should encode + to %2B and give result as {1+6}{7}. Most of the users dont know the URL value for + thus we have to encode it.

UltraInstinct Over a year ago

@IshamMohamed He is actually correct in what he is saying. So a +1 from my side.

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