Issue 6684: "x / 1" and "x * 1" should return x (original) (raw)

Issue6684

Created on 2009-08-11 16:44 by mrjbq7, last changed 2022-04-11 14:56 by admin. This issue is now closed.

Messages (2)
msg91479 - (view)	Author: mrjbq7 (mrjbq7)	Date: 2009-08-11 16:44
There are a couple arithmetic operations that idempotent, where the returned python object is the same python object as the input. For example, given a number: >>> x = 12345 The abs() builtin returns the same number object if it is already a positive value: >>> id(x) 17124964 >>> id(abs(x)) 17124964 The "multiply by zero" operation returns a single "zero" object: >>> id(x * 0) 16794004 >>> id(x * 0) 16794004 But, the "multiply by 1" or "divide by 1" does not: >>> id(x * 1) 17124928 >>> id(x * 1) 17124880 >>> id(x / 1) 17203652 >>> id(x / 1) 17124952
msg91480 - (view)	Author: Raymond Hettinger (rhettinger) *	Date: 2009-08-11 16:56
Sorry, Python makes no guarantees about object identity for numbers, so this is just an optimization request. While it could save a little space (one number object) and a little time (for allocating that object), the special casing imposes a small (but non-zero) cost on every other case for multiplication and division -- optimizing one corner case at the expense of the general case. * practicality beat purity * special cases are not special enough ...