Pass a Boolean String Query to Django

Question

I have a text area that lets a user build their own string which may look like any mix of AND OR NOT between words

ex:

"'disease' AND 'chemical' OR 'toxic' NOT 'imflammation' AND ('foo' OR 'bar')"

They are able to add words from a list, can click the appropriate button to add the AND OR NOT, and add parenthesis. So a string like that is what will be passed from my javascript to Django for me to parse/format to make a query. I can't find much about building a Django query that will handle boolean queries like that though. I don't really know where to start. I'm running MySQL on the backend too. Thanks for any help!

edit: the table I'm querying has a text column and the search will be directed at that. I'm trying to avoid doing a raw sql search in Django. I'm currently searching for things that can either convert any MySQL query to the appropriate Django query or ways to take a string and build a Django query directly from the string (the parenthesis are the hard part I think).

is this for search purpose? is so, haystack is the easiest to get started with. here is the query api: django-haystack.readthedocs.org/en/latest/searchquery_api.html — user2707389
– user2707389, Commented May 18, 2015 at 15:38

jacekbj · Accepted Answer · 2015-05-18 16:49:49Z

2

I assume that you have a set values stored in database, which are boolean values. If so, take a look at pyparsing. You could use simple string substitution to make the query parsable and build an expression. Then you can substitute variables with values fetched from database and evaluate it.

from sympy.parsing.sympy_parser import parse_expr
from sympy import symbols

# define all your symbols
A, B, C, D = symbols('A,B,C,D')
a, b, c, d = fetch_from_database()

user_expr_str = '(A & B) | C' # Change AND to &, OR to | and so on...
try:
    expr = parse_expr(user_expr_str)
except SyntaxError:
    # Do sth with error like return
# Evaluate the expression using data from DB
result = e.subs({A: a, B: b, C: c, D: d})

In the last line you can put all values, not only the ones used in expression.

Worth to mention, building query from user input could expose you to SQL injections and this solution is free of such danger.

answered May 18, 2015 at 16:49

jacekbj

6413 silver badges10 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

sp_conway Over a year ago

Do you mean are the items I am searching for boolean values? I have an extremely large database and I'm doing a string search for each word the user added to the string ex: "wordOne OR wordTwo AND wordThree" and returning a string. I've expanded my original question to add more detail.

sp_conway · Accepted Answer · 2015-05-20 15:32:53Z

0

I found an answer in pyparsing and a script called simpleBool which let me send a string from my HTML textarea of the format from my question to Django and I was able to make Q objects that way. pyparsing is great and simpleBool helped a lot I suggest it for anyone looking to dynamically build queries which may consist of nested queries.

answered May 20, 2015 at 15:32

sp_conway

1071 silver badge11 bronze badges

1 Comment

Elias Prado Over a year ago

The link does not exist anymore.

Collectives™ on Stack Overflow

Pass a Boolean String Query to Django

2 Answers 2

1 Comment

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related