Python offers many inbuild logarithmic functions under the module “math” which allows us to compute logs using a single line. There are 4 variants of logarithmic functions, all of which are discussed in this article.
1. log[a,[Base]] : This function is used to compute the natural logarithm [Base e] of a. If 2 arguments are passed, it computes the logarithm of the desired base of argument a, numerically value of
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 if a negative no. is passed as argument.
Python3
import
math
print
[
"Natural logarithm of 14 is : "
, end
=
""]
print
[math.log[
14
]]
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 compute the logarithm base 2 of a. Displays 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 if a negative no. is passed as argument.
Python3
import
math
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 compute the logarithm base 10 of a. Displays 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 if a negative no. is passed as argument.
Python3
import
math
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 compute logarithm[1+a] .
Syntax : math.log1p[a] Parameters : a : The numeric value Return Value : Returns log[1+a] Exceptions : Raises ValueError if a negative no. is passed as argument.
Python3
import
math
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 value error if number is negative.
Python3
import
math
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 Application
One of the application of log10[] function is that it is used to compute the no. of digits of a number. Code below illustrates the same.
Python3
import
math
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 is contributed by
Manjeet Singh. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to . See your article appearing on the GeeksforGeeks main page and help other Geeks.
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