在Python中使用变量修改参数名称

Question

I'm translating PHP code to Python code which inserts data into a MySql table.

There are four possible columns based on a naming convention: image_ + [hq,sq, lq, thumb] + _url

The php code is as follows (using Laravel DB Query):

DB::table('items')
                ->insertGetId(array(
                   'title' => $title,
                    'image_' . $quality . '_url' => $amazon_url,
                ));

The corresponding python code (using SqlAlchemy Core) which is giving me a syntax error:

item_ins = items_tbl.insert().values(title=item_title, 
                                                   image_+quality+_url=amazon_url

            )

How can I accomplish the same result in Python without reverting to if/else statements?

Answer 1

You can't have variably named keyword arguments in a Python function call. However, you can expand a dict into keyword arguments:

item_ins = items_tbl.insert().values(**{'title' : item_title,
                                        'image_'+quality+'_url' : amazon_url})

If quality=='hq' for example, this is equivalent to calling

item_ins = items_tbl.insert().values(title = item_title,
                                     image_hq_url: amazon_url)

You should also note that in the syntax you tried to use, you tried to treat image_ and _url as string literals and quality as a variable, without making any syntactic distinction between them. There's no way that would work.