math

The :mod:`math` module has been updated with five new functions inspired by the

C99 standard.

The :func:`~math.isfinite` function provides a reliable and fast way to detect

special values. It returns *True* for regular numbers and *False* for *Nan* or

*Infinity*:

>>> [isfinite(x) for x in (123, 4.56, float('Nan'), float('Inf'))]

The :func:`~math.expm1` function computes ``e**x-1`` for small values of *x*

without incuring the loss of precision that usually accompanies the subtraction

of nearly equal quantities:

>>> expm1(0.013671875) # more accurate way to compute e**x-1 for a small x

The :func:`~math.erf` function computes a probability integral of `Gaussian

error function <http://en.wikipedia.org/wiki/Error_function>`_:

>>> erf(1.0/sqrt(2.0)) # portion of normal distribution within 1 standard deviation

:func:`~math.gamma` is a continuous extension of the factorial function. See

http://en.wikipedia.org/wiki/Gamma_function for details. Because the function

is related to factorials, it grows large even for small values of *x*, so there

is also a :func:`~math.lgamma` for computing the natural logarithm of the gamma

function:

>>> gamma(7.0) # six factorial

>>> lgamma(801.0) # log(800 factorial)

(Contributed by Mark Dickinson.)