How do I find the difference between two values without knowing which is larger

Question

I was wondering if there was a function built into Python that can determine the distance between two rational numbers but without me telling it which number is larger  e g    gt  gt  gt distance 6 3  3  gt  gt  gt distance 3 6  3   Obviously I could write a simple definition to calculate which is larger and then just do a simple subtraction   def distance x  y       if x  gt   y          result   x - y     else          result   y - x     return result   but I d rather not have to call a custom function like this  From my limited experience I ve often found Python has a built in function or a module that does exactly what you want and quicker than your code does it  Hopefully someone can tell me there is a built in function that can do this

User · Answer

Just use abs x - y   This ll return the net difference between the two as a positive value  regardless of which value is larger

User · Answer

use this function   its the same convention you wanted  using the simple abs feature of python   also - sometimes the answers are so simple we miss them  its okay      gt  gt  gt  def distance x y       return abs x-y

User · Answer

abs x-y  will do exactly what you re looking for   In  1   abs 1-2  Out 1   1  In  2   abs 2-1  Out 2   1

User · Answer

If you have an array  you can also use numpy diff   import numpy as np a    1 5 6 8  np diff a  Out  array  4  1  2

User · Answer

If you plan to use the signed distance calculation snippet posted by phi  like I did  and your b might have value 0  you probably want to fix the code as described below   import math  def distance a  b       if  a    b           return 0     elif  a  lt  0  and  b  lt  0  or  a  gt  0  and  b  gt   0     fix  b  gt   0 to cover case b    0         if  a  lt  b               return  abs abs a  - abs b            else              return - abs abs a  - abs b        else          return math copysign  abs a    abs b   b    The original snippet does not work correctly regarding sign when a   0 and b    0

User · Answer

If you don t need a signed integer  this is an alternative that uses a slightly different approach  is easy to read and doesn t require an import   def distance a  b     if a  gt  0 and b  gt  0      return max a  b  - min a  b    elif a  lt  0 and b  lt  0      return abs a - b    elif a    b      return 0   return abs a - 0    abs b - 0

User · Answer

This does not address the original question  but I thought I would expand on the answer zinturs gave  If you would like to determine the appropriately-signed distance between any two numbers  you could use a custom function like this   import math  def distance a  b       if  a    b           return 0     elif  a  lt  0  and  b  lt  0  or  a  gt  0  and  b  gt  0           if  a  lt  b               return  abs abs a  - abs b            else              return - abs abs a  - abs b        else          return math copysign  abs a    abs b   b   print distance 3 -5      -8  print distance -3 5       8  print distance -3 -5      2  print distance 5 3       -2  print distance 5 5        0  print distance -5 3       8  print distance 5 -3      -8   Please share simpler or more pythonic approaches  if you have one

User · Answer

abs function is definitely not what you need as it is not calculating the distance  Try abs  -25 15  to see that it s not working  A distance between the numbers is 40 but the output will be 10  Because it s doing the math and then removing  minus  in front  I am using  this custom function    def distance a  b       if  a  lt  0  and  b  lt  0  or  a   0  and  b   0           return abs  abs a  - abs b        if  a  lt  0  and  b   0  or  a   0  and  b  lt  0           return abs  abs a    abs b     print distance -25  -15  print distance 25  -15  print distance -25  15  print distance 25  15

User · Answer

So simple just use abs  a  -  b     will work seamless without any additional care in signs positive   negative   def get distance p1 p2        return abs  p1  -  p2    get distance 0 2  2  get distance 0 2  2  get distance -2 0  2  get distance 2 -1  3  get distance -2 -1  1

User · Answer

Although abs x - y  or equivalently abs y - x  is preferred  if you are curious about a different answer  the following one-liners also work   max x - y  y - x   -min x - y  y - x   max x  y  - min x  y    x - y    math copysign 1  x - y   or equivalently  d    x - y    math copysign 1  d  in Python  3 8  functools reduce operator sub  sorted  x  y   reverse True

User · Answer

You can try  a  0 1 2 3 4 5 6 7 8 9     abs x 1 -x 0   for x in zip a 1   a  -1

[python] How do I find the difference between two values without knowing which is larger?

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