DecInt is a class that support arithmetic on very large decimal integers.
For example, it can calculate the decimal form of the 42nd Mersenne prime, all 7,816,230 digits, in less than 21 seconds. And less than 6 seconds if gmpy 1.01 is available.
This version is significantly faster than the prior version.
Multiplication used a combination of 4-way Toom-Cook and Nussbaumer convolution. Pure Python multiplication is less than 10x slower than GMP's hand optimised assembler code!
Division uses a new algorithm based on David M. Smith's division algorithm. Pure Python division is 16x slower than GMP but can actually be faster in some instances; for example, dividing a 2,000,000 digit number by an 800,000 digit number.
DecInt can be found at http://home.comcast.net/%7Ecasevh/
(DecInt used to be called BigDecimal; I renamed it to avoid confusion with the "decimal" class include with Python.)