Obviously, it would be better to convert numbers to strings once only.

This will work in the mentionned case since, in Python, "0" != 0.

Note that this solution will transform 0.0s into 0s, but in Python this shouldn't be a problem.

Exactly!

Read about python's boolean operations here.

In the context of Boolean operations, and also when expressions are used by control flow statements, the following values are interpreted as false: False, None, numeric zero of all types, and empty strings and containers (including strings, tuples, lists, dictionaries, sets and frozensets). All other values are interpreted as true.

In a list comprehension an if can be added which will cause only those elements which satisfy the if condition to be added to the list.