quantiphy-eval 0.1.0

calculations with physical quantities

Author:

Ken Kundert

Version:

0.1.0

Released:

2020-03-06

A companion to QuantiPhy, quantiphy_eval evaluates strings that contains a simple algebraic expression that involves quantities and returns a quantity. For example:

>>> from quantiphy_eval import evaluate

>>> average = evaluate('($1.2M + $1.3M)/2', '$')
>>> print(f'{average}')
$1.25M

>>> f_avg = evaluate('(122.317MHz + 129.349MHz)/2', 'Hz')
>>> print(f'{f_avg}')
125.83 MHz

With QuantiPhy the units do not survive operations, so you can specify the resolved units using the second argument.

QuantiPhy Eval provides three constants built-in: pi, tau, and e. However, you can pass in additional constants:

>>> from quantiphy import Quantity

>>> my_constants = dict(
...     k = Quantity('k'),
...     q = Quantity('q'),
...     T = Quantity('25°C', scale='K'),
... )
>>> vt = evaluate('k*T/q', 'V', constants=my_constants)
>>> print(vt)
25.693 mV

QuantiPhy Eval provides the following functions built-in: sin, cos, tan, sqrt, abs, trunc, round and sgn. However, you can pass in additional functions:

>>> def median(*args):
...    args = sorted(args)
...    l = len(args)
...    m = l//2
...    if l % 2:
...        return args[m]
...    return (args[m] + args[m-1])/2

>>> my_functions = dict(median=median)
>>> median_price = evaluate('median($636122, $749151, $706781)', '$', functions=my_functions)
>>> print(median_price.fixed(show_commas=True))
$706,781

Finally, QuantiPhy Eval provides rm_commas function for removing commas from an expression. Using it would prevent you from using multi-argument functions, however it would allow you to have commas in your numbers:

>>> from quantiphy_eval import evaluate, rm_commas

>>> average_price = evaluate(rm_commas('($636,122 + $749,151 + $706,781)/3'), '$')
>>> print(average_price.fixed(show_commas=True, prec=2, strip_zeros=False))
$697,351.33

Releases

Latest development release:

Version: 0.1.0

Released: 2020-03-06

0.1 (2019-09-03):

• Add support for user-defined constants and functions.

• add rm_commas function.

0.0 (2020-02-14):

Initial version.