Performing regex Queries with pymongo

Question

I am trying to perform a regex query using pymongo against a mongodb server. The document structure is as follows

{
  "files": [
    "File 1",
    "File 2",
    "File 3",
    "File 4"
  ],
  "rootFolder": "/Location/Of/Files"
}

I want to get all the files that match the pattern *File. I tried doing this as such

db.collectionName.find({'files':'/^File/'})

Yet i get nothing back , am i missing something because according to the mongodb docs this should be possible. If I perform the query in the mongo console it works fine , does this mean the api doesnt support it or am I just using it incorrectly

Answer 1

Turns out regex searches are done a little differently in pymongo but is just as easy.

Regex is done as follows :

db.collectionname.find({'files':{'$regex':'^File'}})

This will match all documents that have a files property that has a item within that starts with File

Answer 2

If you want to include regular expression options (such as ignore case), try this:

import re
regx = re.compile("^foo", re.IGNORECASE)
db.users.find_one({"files": regx})

Answer 3

To avoid the double compilation you can use the bson regex wrapper that comes with PyMongo:

>>> regx = bson.regex.Regex('^foo')
>>> db.users.find_one({"files": regx})

Regex just stores the string without trying to compile it, so find_one can then detect the argument as a 'Regex' type and form the appropriate Mongo query.

I feel this way is slightly more Pythonic than the other top answer, e.g.:

>>> db.collectionname.find({'files':{'$regex':'^File'}})

It's worth reading up on the bson Regex documentation if you plan to use regex queries because there are some caveats.

Answer 4

The solution of re doesn't use the index at all. You should use commands like:

db.collectionname.find({'files':{'$regex':'^File'}})

( I cannot comment below their replies, so I reply here )

Answer 5

import re

def get_pattern_query(pattern,starting_with=False,ending_with=False,ignore_case=False):
    start = '^' if starting_with else '.*'
    end = '$' if ending_with else '.*'
    pattern = start + re.escape(pattern) + end
    return re.compile(pattern, re.IGNORECASE) if ignore_case else re.compile(pattern)

Escaping the pattern before compiling handles all characters.