Python math library | expm1() method

Python has math library and has many functions regarding to it. One such function is expm1(). This function mathematically computes the value of exp(x) - 1. This method can be used if we need to compute this very value.

Syntax : math.expm1()

Parameters :
x : Number whose exp(x)-1 has to be computed.

Returns : Returns the computed value of “exp(x)-1”

Code #1 : Demonstrate the working of expm1()

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# Python3 code to demonstrate
# the working of expm1()
import math
  
# initializing the value 
test_int = 4
test_neg_int = -3
  
# checking expm1() values
# doesn't throw error with negative
print ("The expm1 value using positive integer : "
                      + str(math.expm1(test_int)))
                        
print ("The expm1 value using negative integer : "
                  + str(math.expm1(test_neg_int)))

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Output :


The expm1 value using positive integer : 53.598150033144236
The expm1 value using negative integer : -0.950212931632136


 


“exp() – 1” vs “expm1()”


There would be a question why expm1() method was even created if we could always compute exp() and then subtract 1 from it. The first reason is that value exp() - 1 is used a lot in mathematics and science applications and formulas.

The most important reason is that for smaller value of x, of the order less than e-10, expm1() method give a result more accurate than exp() - 1.


Code #2 : Comparing expm1() and  exp()-1











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# Python3 code to demonstrate 


# the application of expm1() 


import math 


  


# initializing the value  


test_int = 1e-10


  


# checking expm1() values 


# expm1() is more accurate 


print ("The value with exp()-1  : " + str(math.exp(test_int)-1)) 


print ("The value with expm1() : " + str(math.expm1(test_int))) 



















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Output :


The value with exp()-1  : 1.000000082740371e-10
The value with expm1() : 1.00000000005e-10




          
          
          
          

            

    

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