Python - abs vs fabs

Question

I noticed that in python there are two similar looking methods for finding the absolute value of a number   First  abs -5    Second  import math math fabs -5    How do these methods differ

User · Accepted Answer

math fabs   converts its argument to float if it can  if it can t  it throws an exception   It then takes the absolute value  and returns the result as a float  In addition to floats  abs   also works with integers and complex numbers  Its return type depends on the type of its argument  In  7   type abs -2   Out 7   int  In  8   type abs -2 0   Out 8   float  In  9   type abs 3 4j   Out 9   float  In  10   type math fabs -2   Out 10   float  In  11   type math fabs -2 0   Out 11   float  In  12   type math fabs 3 4j   --------------------------------------------------------------------------- TypeError                                 Traceback  most recent call last   home npe  lt ipython-input-12-8368761369da gt  in  lt module gt    ---- gt  1 type math fabs 3 4j    TypeError  can t convert complex to float

User · Answer

math fabs   always returns float  while abs   may return integer

User · Answer

abs      Returns the absolute value as per the argument i e  if argument is int then it returns int  if argument is float it returns float   Also it works on complex variable also i e  abs a bj  also works and returns absolute value i e math sqrt   a   2    b   2   math fabs      It only works on the integer or float values  Always returns the absolute float value no matter what is the argument type except for the complex numbers

User · Answer

Edit  as  aix suggested  a better  more fair  way to compare the speed difference    In  1    timeit abs 5  10000000 loops  best of 3  86 5 ns per loop  In  2   from math import fabs  In  3    timeit fabs 5  10000000 loops  best of 3  115 ns per loop  In  4    timeit abs -5  10000000 loops  best of 3  88 3 ns per loop  In  5    timeit fabs -5  10000000 loops  best of 3  114 ns per loop  In  6    timeit abs 5 0  10000000 loops  best of 3  92 5 ns per loop  In  7    timeit fabs 5 0  10000000 loops  best of 3  93 2 ns per loop  In  8    timeit abs -5 0  10000000 loops  best of 3  91 8 ns per loop  In  9    timeit fabs -5 0  10000000 loops  best of 3  91 ns per loop   So it seems abs   only has slight speed advantage over fabs   for integers  For floats  abs   and fabs   demonstrate similar speed     In addition to what  aix has said  one more thing to consider is the speed difference    In  1    timeit abs -5  10000000 loops  best of 3  102 ns per loop  In  2   import math  In  3    timeit math fabs -5  10000000 loops  best of 3  194 ns per loop   So abs   is faster than math fabs

[python] Python - abs vs fabs

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