import sys
from PyQt5.QtWidgets import QApplication, QWidget, QPushButton, QLabel
from PyQt5.QtWidgets import QLineEdit, QTableWidget, QTableWidgetItem
from math import sin, cos, tan

class MainWidget(QWidget):
    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        self.setGeometry(100, 100, 300, 400)

        self.eq_label = QLabel(self)
        self.eq_label.setText('Введите уравнение:')
        self.eq_label.move(80, 30)

        self.eq_gap = QLineEdit(self)
        self.eq_gap.move(80, 60)

        self.equation = [] #коэф уравнения от пустого до старшего

        self.solve_btn = QPushButton('Решить', self)
        self.solve_btn.resize(self.solve_btn.sizeHint())
        self.solve_btn.move(75, 100)
        self.solve_btn.clicked.connect(self.build_eq)

    def add_eq(self, ind, val): #добавляем в equation коэф val степени ind
        if len(self.equation) <= ind:
            ln = len(self.equation)
            for i in range(ind - ln + 1):
                self.equation.append(0)
        self.equation[ind] += val

    def build_eq(self): #разбиваем уравнение на левую/правую части и вызываем get_eq
        s = ''.join(self.eq_gap.text().split())
        if not len(s):
            return
        h = s.split('=')
        left, right = h[0], h[1]
        self.get_eq(left, 1)
        self.get_eq(right, -1)
        self.solve()

    def get_eq(self, s, global_sign): #из строки с многочленом строим equation
        l = 0
        while l < len(s):
            sign = global_sign
            if s[l] in '+-':
                if s[l] == '-':
                    sign *= -1
                l += 1
            val = 0
            while l < len(s) and s[l].isdigit():
                val += int(s[l])
                val *= 10
                l += 1
            if val > 10:
                val //= 10
            val *= sign
            if (l == len(s)) or (not s[l].isalpha()):
                self.add_eq(0, val)
                continue
            l += 1
            if l == len(s) or s[l] != '^':
                self.add_eq(1, val)
            l += 1
            st = 0
            while l < len(s) and s[l].isdigit():
                st += int(s[l])
                st *= 10
                l += 1
            st /= 10
            self.add_eq(st, val)

    def f(self, x): #f(x)
        ret = 0
        for i in range(len(self.equation)):
            ret += self.equation[i] + x ** i
        return ret

    def solve(self):
        pass



if __name__ == '__main__':
    app = QApplication(sys.argv)
    wid = MainWidget()
    wid.show()
    sys.exit(app.exec())