[New-bugs-announce] [issue1880] Generalize math.hypot function
David W. Lambert
report at bugs.python.org
Mon Jan 21 03:58:52 CET 2008
New submission from David W. Lambert:
Please generalize math.hypot. While I don't have a survey of python
codes, it seems to me unlikely for this change to break existing
programs.
import math
def hypot(*args):
'''
Return the Euclidean vector length.
>>> from math import hypot, sqrt
>>> hypot(5,12) # traditional definition
13.0
>>> hypot()
0.0
>>> hypot(-6.25)
6.25
>>> hypot(1,1,1) == sqrt(3) # diagonal of unit box
True
'''
return math.sqrt(sum(arg*arg for arg in args))
I propose this version as closest to:
>>> print sys.version
2.5.1 (r251:54863, Jan 4 2008, 17:15:14)
[GCC 3.4.4 (cygming special, gdc 0.12, using dmd 0.125)]
>>> print math.hypot.__doc__
hypot(x,y)
Return the Euclidean distance, sqrt(x*x + y*y).
Thanks,
Dave.
PS. I don't understand why python is so restrictive. Although hypot
is in the math library, it could be written in EAFP style as
def hypot(*args):
return sum(arg*arg for arg in args)**0.5
Rather than review the entire python library for items to generalize,
I'll accept that the resulting errors would confuse "the penguin on my
tele". "hypot" crosses me most often. I've not yet needed a version
in the complex domain, such as my second version.
I typically fill my need for length with scipy.sqrt(scipy.dot(v,v)),
only to realize that for the short vectors I use, standard python
constructs always perform faster than scipy
----------
components: Library (Lib)
messages: 61374
nosy: LambertDW
severity: minor
status: open
title: Generalize math.hypot function
type: rfe
versions: Python 3.0
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<http://bugs.python.org/issue1880>
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