[Python-Dev] PEP 8 updated on whether to break before or after a binary update (original) (raw)

Tim Peters tim.peters at gmail.com
Fri Apr 15 13:02:43 EDT 2016

[Guido]

After a fruitful discussion on python-ideas I've decided that it's fine to break lines before a binary operator. It looks better and Knuth recommends it. ... Therefore 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 is suggested.

Some examples of code breaking before binary Boolean operators:: class Rectangle(Blob): def init(self, width, height, color='black', emphasis=None, highlight=0): if (width == 0 and height == 0 and color == 'red' and emphasis == 'strong' or highlight > 100): raise ValueError("sorry, you lose") if (width == 0 and height == 0 and (color == 'red' or emphasis is None)): raise ValueError("I don't think so -- values are %s, %s" % (width, height)) Blob.init(self, width, height, color, emphasis, highlight)

Note that this code still breaks a line after a binary operator (the string formatting "%" operator in the 2nd ValueError call). But it's perfectly clear the way it is. Good taste can't be reduced to rules ;-)

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