CODEWITHSUNDEEP
pythonpython-3.x
Don Draper
Don Draper

Reputation: 541

Boolean operations in Python (notation in the docs)

I'm not a novice programmer and I know what booleans are and how to use them. Trouble is, I can't quite understand what is implied in Python's documentation regarding boolean operations:

or_test  ::=  and_test | or_test "or" and_test
and_test ::=  not_test | and_test "and" not_test
not_test ::=  comparison | "not" not_test

What does all this recursion mean? Why should there be an "and_test" inside of an or_test? The same question about "not_test" in the description of and_test The third line makes even less sense to me. Could anyone please guide me through these lines so that I can finally understand this somewhat unnecessarily recursive and tangled notation

Upvotes: 2

Views: 179

Answers (1)

Martijn Pieters
Martijn Pieters

Reputation: 1124170

This is part of the larger language grammar and in essence specifies the operator precedence.

It means that and binds tighter than or does. Note that or_test does not have to contain and, it contains the and_test rule, which is constructed from either an not_test rule or and_test "and" not_test. not_test itself constructed in a similar manner, etc.

Also see the Notation section of the reference documentation.

Upvotes: 2

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