CODEWITHSUNDEEP
pythonpow
mark T
mark T

Reputation: 243

calculate mod using pow function python

So, If i would like to calculate the value of 6^8 mod 5 using the pow function, what should I put in a line??

In the assumption that You don't need to import it first

I know that pow is used like pow (x, y) = pow (6, 8) = 6^8 and

My guess is 

mod.pow(6,8)

Thank you!

Upvotes: 22

Views: 46692

Answers (3)

Syed Ashraf
Syed Ashraf

Reputation: 17

You can use '%' character to get the modulo value. For example print(pow(6,8) % 5) or print(6**8 % 5).

Upvotes: 0

hiro protagonist
hiro protagonist

Reputation: 46921

check the docs of pow:

pow(6, 8, 5)

does what you want.

do not use a ** b % n! while this will give the correct result it will be by orders of magnitude slower if you do calculations for bigger numbers. pow will do the modulo operation in every step while ** will first do the exponentiation in the integers (which may result in a huge number) and take the modulus only at the end.

now if you are interested in numbers that are bigger than 32 bit you may want to have a look at gmpy2 for even more speed.

Upvotes: 9

PM 2Ring
PM 2Ring

Reputation: 55509

It's simple: pow takes an optional 3rd argument for the modulus.

From the docs:

pow(x, y[, z])

Return x to the power y; if z is present, return x to the power y, modulo z (computed more efficiently than pow(x, y) % z). The two-argument form pow(x, y) is equivalent to using the power operator: x**y.

So you want:

pow(6, 8, 5)

Not only is pow(x, y, z) faster & more efficient than (x ** y) % z it can easily handle large values of y without using arbitrary precision arithmetic, assuming z is a simple machine integer.

Upvotes: 47

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