Example of implicit line continuation:
a = some_function(
'1' + '2' + '3' - '4')
On the topic of line-breaks around a binary operator, it goes on to say:-
For decades the recommended style was to break after binary operators. But this can hurt readability in two ways: the operators tend to get scattered across different columns on the screen, and each operator has moved away from its operand and onto the previous line.
In Python code, it is permissible to break before or after a binary operator, as long as the convention is consistent locally. For new code Knuth's style (line breaks before the operator) is suggested.
Example of explicit line continuation:
a = '1' \
+ '2' \
+ '3' \