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# Log functions in Python

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1. log (a, (Base)): this function is used to calculate the natural logarithm (Base e) for a. If 2 arguments are passed, it computes the logarithm of the required base of argument a, the numerical value log (a) / log (Base) .

`  Syntax:  math. log (a, Base)  Parameters:   a:  The numeric value  Base:  Base to which the logarithm has to be computed.  Return Value:  Returns natural log if 1 argument is passed and log with specified base if 2 arguments are passed.  Exceptions:  Raises ValueError is a negative no. is passed as argument. `

` `

` # Python code to demonstrate how it works # log (a, Base)   import math   # Print database of 14 e logs print ( "Natural logarithm of 14 is:" , end = "") print (math.log ( 14 ))   # Print database 5 of 14 log print ( " Logarithm base 5 of 14 is: " , end = "") print ( math.log ( 14 , 5 )) `

Output:

` Natural logarithm of 14 is: 2.6390573296152584 Logarithm base 5 of 14 is: 1.6397385131955606 `

2. log2 (a): this function is used to calculate the log base 2 for a. Displays a more accurate result than log (a, 2).

`  Syntax:  math.log2 (a)  Parameters:   a:  The numeric value  Return Value:  Returns logarithm base 2 of a  Exceptions:  Raises ValueError is a negative no. is passed as argument. `

` `

` # Python code to demonstrate how it works # log2 (a)   import math   # Print database 2 of 14 log print ( "Logarithm base 2 of 14 is:" , end = "") print (math.log2 ( 14 )) `

Output:

` Logarithm base 2 of 14 is: 3.807354922057604 `

3. log10 (a): this function is used to calculate the log base 10 for a. Displays a more accurate result than log (a, 10).

`  Syntax:  math.log10 (a)  Parameters:   a:  The numeric value  Return Value:  Returns logarithm base 10 of a  Exceptions:  Raises ValueError is a negative no. is passed as argument. `

` `

` # Python code to demonstrate how it works # log10 (a)   import math   # Print base 10 of 14 log print ( "Logarithm base 10 of 14 is:" , end = "") print (math.log10 ( 14 )) `

Output:

` Logarithm base 10 of 14 is: 1.146128035678238 `

3. log1p (a): this function is used to calculate the logarithm (1 + a) .

`  Syntax:  math.log1p (a)  Parameters:   a:  The numeric value  Return Value:  Returns log (1 + a)  Exceptions:  Raises ValueError is a negative no. is passed as argument. `

` `

` # Python code to demonstrate how it works # log1p (a)   import math   # Print magazine (1 + a) out of 14 print ( "Logarithm (1 + a) value of 14 is: " , end = " ") print (math.log1p ( 14 )) `

Output:

` Logarithm (1 + a) value of 14 is: 2.70805020110221 `

exception

1. ValueError: This function returns a value error if the number is negative .

 ` # Python code to demonstrate the exception ` ` # log (a) `   ` import ` ` math `   ` # Print log (s) -14 ` ` # Throws an exception ` ` print ` ` (` ` "log (a) value of -14 is:" ` `, end ` ` = ` ` "") ` ` print ` ` (math.log (` ` - ` ` 14 ` `)) `` `

Output:

` log (a) value of -14 is: `

Runtime error:

` Traceback (most recent call last): File "/home/8a74e9d7e5adfdb902ab15712cbaafe2.py", line 9, in print (math.log ( -14)) ValueError: math domain error `

Practical use

One use of the log10 () function is that it is used to calculations no. digits of the number . The code below illustrates the same.

 ` # Python code to demonstrate usage ` ` # log10 (a) `   ` import ` ` math `   ` # Print # of digits in 73293 ` ` print ` ` (` ` "The number of digits in 73293 are: "` `, end ` ` = ` `" ") ` ` print ` ` (` ` int ` ` (math.log10 (` ` 73293 ` `) ` ` + ` ` 1 ` `)) `

Output:

` The number of digits in 73293 are: 5 `

This article courtesy of Manjeet Singh . If you are as Python.Engineering and would like to contribute, you can also write an article using contribute.python.engineering or by posting an article contribute @ python.engineering. See my article appearing on the Python.Engineering homepage and help other geeks.

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