A python psycopg2 quirk

psycopg2 is the de-facto Python module to interface with PostgreSQL database but it has a quirk you ought to beware of.

Parameterized query is the recommended way to modify your SQL statement programmatically where you could sprinkle your SQL statement with variable placeholders like %s or %(myvar)s. But, if the statement happens to use any ILIKE operator e.g. '%pattern%', you must escape every occurrence of % in your operand with %%, i.e. '%%pattern%%'. Otherwise psycopg2 will throw the exception error message “argument formats can’t be mixed”.

This feature is actually mentioned in the documentation, http://initd.org/psycopg/docs/usage.html#passing-parameters-to-sql-queries

When parameters are used, in order to include a literal % in the query you can use the %% string