Python math.log1p() Method

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The Python math.log1p() method is used to calculate the natural logarithm of 1 + x, where x is the argument passed to the method. Mathematically, the method is represented as −

\log1p\:(x)\:=\:\log_{e}({1\:+\:x})\:=\:\ln(1\:+\:x)

Where, e is the base of the natural logarithm (Euler's number). For example, if x = 1, then math.log1p(1) returns ln(1 + 1), which simplifies to ln(2).

Note: To use this function, you need to import math module.

Syntax

Following is the basic syntax of the Python math.log1p() method −

math.log1p(x)

Parameters

This method accepts either an integer or a floating-point number as a parameter for which you want to calculate the natural logarithm of 1 plus x.

Return Value

The method returns the natural logarithm of 1 plus x. The return value is a floating-point number.

Example 1

In the following example, we calculate the natural logarithm of 1 + 1, which means passing a positive integer as an argument to the log1p() method −

import math
result = math.log1p(1)
print("The result obtained is:", result)  

Output

The output obtained is as follows −

The result obtained is: 0.6931471805599453

Example 2

Here, we pass a negative integer as an argument to the log1p() method. We calculate the natural logarithm of 1 − 0.5 −

import math
result = math.log1p(-0.5)
print("The result obtained is:", result)  

Output

Following is the output of the above code −

The result obtained is: -0.6931471805599453

Example 3

In this example, we calculate the natural logarithm of 1 + 1000, which is a large number −

import math
result = math.log1p(1000)
print("The result obtained is:", result)  

Output

We get the output as shown below −

The result obtained is: 6.90875477931522

Example 4

Now, we use a variable "x" to store the argument. We then calculate the natural logarithm of 1 + x −

import math
x = 2
result = math.log1p(x)
print("The result obtained is:", result)  

Output

The result produced is as shown below −

The result obtained is: 1.0986122886681096