Python - Math - Algebra and Symbolic Math with SymPy(Solving Single-Variable Inequalities)

Doing Math with Python
邦訳

開発環境

• OS X El Capitan - Apple (OS)
• Emacs (Text Editor)
• Python 3.5 (プログラミング言語)

Doing Math with Python: Use Programming to Explore Algebra, Statistics, Calculus, and More! (Amit Saha (著)、No Starch Press)のChapter 4.(Algebra and Symbolic Math with SymPy)、Programming Challenges #4: Solving Single-Variable Inequalities(No. 2939)を解いてみる。

#4: Solving Single-Variable Inequalities(No. 2939)

コード(Emacs)

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import sympy

def isolve(ineq_obj):
    x = sympy.Symbol('x')
    lhs = ineq_obj.lhs
    rel = ineq_obj.rel_op
    if lhs.is_polynomial():
        p = sympy.Poly(lhs, x)
        rel = ineq_obj.rel_op
        return sympy.solve_poly_inequality(p, rel)
    if lhs.is_rational_function():
        numer, denom = lhs.as_numer_denom()
        p1 = sympy.Poly(numer)
        p2 = sympy.Poly(denom)
        return sympy.solve_rational_inequalities([[((p1, p2), rel)]])
    return sympy.solve_univariate_inequality(ineq_obj, x, relational=False)

if __name__ == '__main__':
    while True:
        expr = input('Enter the inequality expression: ')
        if expr == 'q':
            break
        try:
            ineq_obj = sympy.sympify(expr)
        except sympy.SympifyError as err:
            print(err)
        else:
            print(isolve(ineq_obj))

入出力結果(Terminal, IPython)

$ ./sample4.py
Enter the inequality expression: -x**2 + 4 < 0
[(-oo, -2), (2, oo)]
Enter the inequality expression: ((x-1)/(x+2)) > 0
(-oo, -2) U (1, oo)
Enter the inequality expression: sin(x) - 0.6 > 0
(0.643501108793284, 2.49809154479651)
Enter the inequality expression: q
$