Since there are already keyboard maps for moving a line up / down, duplicating a line and deleting a line, the only goal I would choose for the entire line is to copy too much space to move up / down. Thus, I use the copy command (available by default with Command-C using PyCharm CE 2017.3 on Mac), which has nice behavior when automatically selecting and copying the entire line where the cursor is if there is currently no text selected.
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