Arbitrary-precision multiple-precision floats in Python: mpmath, gmpy, sympy .evalf() / N()
https://en.wikipedia.org/wiki/Arbitrary-precision_arithmetic - https://github.com/fredrik-johansson/mpmath > Python library for arbitrary-precision floating-point arithmetic - docs: http://mpmath.org/doc/current/ - mpmath is used by SymPy and Sage - mpmath uses gmpy if it's installed (otherwise Python ints) - https://github.com/aleaxit/gmpy > General Multi-Precision arithmetic for Python 2.6+/3+ (GMP, MPIR, MPFR, MPC) - docs: https://gmpy2.readthedocs.io/en/latest/ - Integers, Rationals, Reals, Complex https://docs.sympy.org/latest/modules/evalf.html : > Exact SymPy expressions can be converted to floating-point approximations (decimal numbers) using either the .evalf() method or the N() function. > [...] > By default, numerical evaluation is performed to an accuracy of 15 decimal digits. You can optionally pass a desired accuracy (which should be a positive integer) as an argument to evalf or N: >>> N(sqrt(2)*pi, 5) 4.4429 >>> N(sqrt(2)*pi, 50) 4.4428829381583662470158809900606936986146216893757 On Sat, Oct 10, 2020 at 3:34 PM Marco Sulla <marco.sulla.pyt...@gmail.com> wrote: > On Sat, 10 Oct 2020 at 19:28, Tim Peters <tim.pet...@gmail.com> wrote: > > Try to spell out what you mean - precisely! - by "this". I can't do > > that for you. For any plausible way of fleshing it out I've thought > > of, the answer is "no". > > Well, please, don't be so harsh. I'm trying to discuss to someone that > co-created Python itself, it's not simple to me :-P > > > The closest you can get to BigDecimal's behavior "by magic" in Python > > is to set the context precision to its maximum allowed value. > > I think there's another "trick" to get the BigDecimal behaviour. > If you read the Javadoc, it says that each operation has a default > precision. For example, multiplication a*b has precision = a_scale + > b_scale. So, in reality, also BigDecimal has a context with finite > precision. The difference is that the default context has a variable > precision, depending on the operation. > > Could Python decimal have something similar, maybe by setting prec = -1? > _______________________________________________ > Python-ideas mailing list -- python-ideas@python.org > To unsubscribe send an email to python-ideas-le...@python.org > https://mail.python.org/mailman3/lists/python-ideas.python.org/ > Message archived at > https://mail.python.org/archives/list/python-ideas@python.org/message/O7KUARDPTMJ36FEYJTKGEUPHFG3A5BOG/ > Code of Conduct: http://python.org/psf/codeofconduct/ >
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