class Dof:
    def __init__(self, strU_, strF_):
        self.strU = strU_  # essential variable name
        self.strF = strF_  # natural variable name
        self.bryF = lambda t: 0.0    # essential boundary value (python function)
        self.bryU = 0.0    # natural boundary value
        self.eq_id = -1    # equation number related to the global system
        self.presc = False # flag for prescribed essential boundary condition
        self.history  = [[], [], [], [], []]  # saved values of variables along time

class Node:

    def __init__(self):
        self.dofs = []      # list for degrees of freedom
        self.id   = -1      # node identification number
        self.save_history = False # flag for saving history

    def add_dof(self, dof_U, dof_F):
        """ Adds a new degree of freedom """
        # check if dof_U is already contained in dofs list
        found = False
        for dof in self.dofs:
            if dof.strU == dof_U:
                found = True
                break