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# Python log2() Function | How to Use log2() in Python

Python log2(x) is an inbuilt function that is used to get the logarithm of any given number with base 2. The log2(x) function is under the math library, so we need to import the math library to use the log2() function. The Python log2() method is one of the Python Math functions used to calculate the logarithmic value of a provided number of base 2.

## Python log2()

Content Overview

Python math.log2() function is a library method of the math module, it is used to get the base-2 logarithm of a number and it accepts the number and returns the base-2 logarithm of the given number.

### Syntax

`math.log2(number)`

This function takes one argument.

number -> whose log we want to find with base 2.

### Return Value

The log2() function returns the logarithm of base 2 of the specific given number. But this function throws a ValueError exception if any value is passed as an argument.

See the following scenarios of Python log2().

1. If a number argument is the positive number, the log2 function returns the output.
2. If a number argument is the Negative number or Zero, log2 function returns ValueError.
3. If it is not a number, log2() function returns TypeError.

### Programming Example

See the following code.

```# Importing math library
import math

# initializing values

# positive value
num = 10
print("Logarithm with base 2 of the value ", num, " is: ", math.log2(num))

# Negative number
num = -10
print("Logarithm with base 2 of the value ", num, " is: ", math.log2(num))
```

#### Output

```Logarithm with base 2 of the value  10  is:  3.321928094887362
Traceback (most recent call last):
File "log2p1.py", line 12, in <module>
print("Logarithm with base 2 of the value ",num," is: ",math.log2(num))
ValueError: math domain error
```

In this program, we have first initialized the value then we have calculated the logarithm of the number with base 2 and in the next line we wanted to calculate the logarithm of a negative number, but as per rule, the program threw an exception of ValueError.

### Example 2

```# Importing math library
import math

# taking input from user values

# positive value
num = int(input("Enter a num to find log2(): "))
print("Logarithm with base 2 of the value ", num, " is: ", math.log2(num))
```

#### Output

```Enter a num to find log(1+a): 10
Logarithm with base 2 of the value  10  is:  3.321928094887362
```

In this program, we have taken input from the user then we have calculated the logarithm of base 2.

The Python log2() method is more accurate than math.log(x, 2).

## Python log2 with list and tuple

Python log2 method calculates the logarithmic value of the given number of base 2. In this code example, we are going to check the base 2 logarithmic value with different data types and display the output.

```# app.py

import math

Tup = (11, 21, 30, -46, 52)  # Tuple Declaration
Lis = [-1, 2, 3.5, -43, -19]  # List Declaration

print('The log2() value of Positive Number = %.2f' % math.log2(5))
print('The log2() value of Positive Decimal = %.2f' % math.log2(2.5))

print('The log2() value of Tuple Item = %.2f' % math.log2(Tup[2]))
print('The log2() value of List Item = %.2f' % math.log2(Lis[2]))

print('The log2() value of Multiple Number = %.2f' % math.log2(2 + 7 - 5))
print('The log2() value of String Value = ', math.log2('Python'))
```

#### Output

```python3 app.py
The log2() value of Positive Number = 2.32
The log2() value of Positive Decimal = 1.32
The log2() value of Tuple Item = 4.91
The log2() value of List Item = 1.81
The log2() value of Multiple Number = 2.00
Traceback (most recent call last):
File "app.py", line 13, in <module>
print('The log2() value of String Value = ', math.log2('Python'))
TypeError: must be real number, not str```

## See also

Python log(x, base)

Python log1p(x)

Python exp()

Python trunc()

Python absolute value

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