How to find out a^b of very large numbers in python?

Question

I am trying to find out a^b in python, of really large no.s

My code is this:

t=raw_input()
c=[]
for j in range(0,int(t)):
    n=raw_input()
    a=[]
    a,b= (int(i) for i in n.split(' '))
    c.extend(pow(a,b))
for j in c:
    print j

And I am getting an error like this:

raceback (most recent call last):
  File "C:/Python26/lastdig.py", line 7, in <module>
    c.extend(pow(a,b))
TypeError: 'int' object is not iterable

Whats wrong in my prob and is it an efficent way to find out powers of large numbers?

Answer 1

You should try GMPY. Try something like:

import gmpy
a = gmpy.mpz(10**10)
b = a**10000000

I don't know how much "big" your numbers are, this solution isn't that fast (but the result is big enough :P )

Answer 2

Another way you might want to try calculating exponents is by using logarithm laws.

x^y = e^(y ln x)

I can't say for certain but this might reduce the number of operations required to calculate large exponents.

Answer 3

python integer ops are arbitrary precision If you want arbitrary precision floating point ops import Decimal

from decimal import *
d=Decimal('2.0')
print d**1234

Answer 4

10000**10000 prints in my machine in under a second.

How large is your input.

Your problem is not related to power function.

Use

c.append()

instead of

c.extend()

c.extend takes an iterable (a list/tuple/set/custom iterables) as an input.

Answer 5

You are using extend wrong. A.extend( B ), requires that B is some iterable object( ie a list, tuple ). You really want to use append instead.

t=raw_input()
c=[]
for j in range(0,int(t)):
    n=raw_input()
    a,b= (int(i) for i in n.split(' '))
    c.append( pow(a,b) ) ## or you could extend c.extend( [ pow(a,b) ] ), but thats silly.
for j in c:
    print j