在列表理解中创建动态键

Question

I am using sqlalchemy(core) to extract primary key column(s) from an alchemy table. So in essence I do this initially:

coupon_tbl = db.Table( "issued_coupon", metadata, autoload=True, autoload_with=engine, schema="pricer"

Now in order to extract the primary key columns, I iterate over the corresponding object like this:

pk_tuple = []
for x in coupon_tbl.primary_key.columns._all_columns:

    pk_tuple.append(x.name)

pk_tuple = tuple(pk_tuple)

Now what I would like to do is to create a dictionary that has the a tuple of keys as the dictionary key like so:

for rec in batchrecordlist:

    batchrecorddict[(rec["user_id"], rec["timestamp"])] = rec

But how do I do this dynamically? I want something like this:

batchrecorddict["expansion of tuple perhaps?"] = rec. So if there were in fact 3 columns to the primary key, then the assignment would look like this:

batchrecorddict[(rec["user_id"], rec["timestamp"], rec["3rd column of key])] = rec etc...

Can this be done?

Answer 1

I figured it out, pretty simply actually:

Create this function:

def renderPKtuple(rec, pkcolumn): tmplist = []

for x in pkcolumn:
    tmplist.append(rec[x])

return tuple(tmplist)

And then in the loop call it this way:

for rec in batchrecordlist:

    batchrecorddict[renderPKtuple(rec, pk_tuple)] = rec