Question

I try to execute essentially some sql like this (which gets builded in a complicated way):

sql = "SELECT COUNT(*) FROM entities WHERE (unit = '%')"

with this Python code:

engine.execute(sql)

What happens then is I get a

TypeError: 'dict' object does not support indexing

Why is this the case?

Answer 1

Not 100% sure, but I think SQLAlchemy is trying to intepret the % character as a SQL parameter. I’d try doubling the % character to work around this:

sql = "SELECT COUNT(*) FROM entities WHERE (unit = '%%')"

This depends on what database you are using; different database adapters use different parameter styles. The psycopg2 module, used for PostgreSQL database connections, for example uses the %s style and documents that %% is the correct way to insert a % literal value into your SQL statements.