Python math.log2() Method

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The Python math.log2() method is used to calculate the base-2 logarithm of a given number x. It calculates the power to which 2 must be raised to obtain x. Mathematically, the method is represented as −

\log2\:(x)\:=\:\log_{2}({x})

In other words, if log2(x) = y, then 2^y = x. For example, if x = 8, then math.log2(8) returns 3 because 2³ = 8.

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

Syntax

Following is the basic syntax of the Python math.log2() method −

math.log2(x)

Parameters

This method accepts either an integer or a floating-point number as a parameter for which you want to calculate the logarithm base 2.

Return Value

The method returns the logarithm base 2 of x. The return value is a floating-point number.

Example 1

In the following example, we calculate the base-2 logarithm of 8, which means passing a positive integer as an argument to the log2() method −

import math
result = math.log2(8)
print("The result obtained is:", result)  

Output

The output obtained is as follows −

The result obtained is: 3.0

Example 2

Here, we pass a fractional value as an argument to the log2() method. We calculate the base-2 logarithm of 0.5 −

import math
result = math.log2(0.5)
print("The result obtained is:", result)  

Output

Following is the output of the above code −

The result obtained is: -1.0

Example 3

In this example, we calculate the base-2 logarithm of 3. Since 3 is not a power of 2, the result is a decimal value −

import math
result = math.log2(3)
print("The result obtained is:", result)  

Output

We get the output as shown below −

The result obtained is: 1.584962500721156

Example 4

Now, we use a variable "x" to store the argument. We then calculate the base-2 logarithm of 16 −

import math
x = 16
result = math.log2(x)
print("The result obtained is:", result)  

Output

The result produced is as shown below −

The result obtained is: 4.0