# 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()

 `# 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))) `

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

 `# 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))) `

Output :

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