Polynomial-Derivative-Python Getting a polynomial's derivative using regex in python. ##How it works The input polynomial string is divided into an array of coefficients and an array of corresponding powers. Each coefficient is multiplied by the power and each power is decremented by one. (Simple derivativation) At the end the new coefficients a…

poly_derivative.py

import re

def derivative(polynomial):

	coefficient = re.findall(r'-?[\d]*[x$]', polynomial)

	power = re.findall(r'[\^][-]?[\d$]+', polynomial)

	derivative_polynomial = []

	# print coefficient
	# print power

	for i in range(len(coefficient)):
		coef = re.findall(r'[-\d]+',coefficient[i])
		if len(coef) != 0:
			if coef[0]=='-':
				coef[0] = '-1'
			a = int(coef[0])
		else: a=1
		b = 1
		if i < len(power):
			b = int(power[i][1:])
		derivative = a*b

		if b>2:
			end = '^'+str(b-1)
		elif b<0: end = '^' + str(b-1)
		else: end=''

		# print "a: " + str(a)
		# print "b: " + str(b)
		# sys.stdout.softspace=0

		# print("+"*(derivative>0 and i!=0) +str(derivative)+ 'x'*(abs(b-1)>0)+end),
		derivative_polynomial.append("+"*(derivative>0 and i!=0) + str(derivative)+ 'x'*(abs(b-1)>0)+end)
	if len(derivative_polynomial)==0: derivative_polynomial.append('0')
	return "".join(derivative_polynomial)

assert getDerivative("4x+1"),"4"
assert getDerivative("-4x-1"),"-4"
assert getDerivative("x^2+2x+1"),"2x+2"
assert getDerivative("0"),"0"
assert getDerivative("-100"),"0"
assert getDerivative("-x^2+3x+4"),"-2x+3"
assert getDerivative("-x^5-x^4-x^3"),"-5x^4-4x^3-3x^2"
assert getDerivative("10x^9+10x^3+10x"),"90x^8+30x^2+10"
assert getDerivative("100x^5+12x^3-3x-3"),"500x^4+36x^2-3"
assert getDerivative("-1000x^7+200x^4+6x^2+x+1000"),"-7000x^6+800x^3+12x+1"