for x in range(1, 5):
    self.entryplot_valx.delete(0, tk.END)

self.entryplot_val1.delete(0, tk.END)
    self.entryplot_val2.delete(0, tk.END)
    self.entryplot_val3.delete(0, tk.END)
    self.entryplot_val4.delete(0, tk.END)

for x in range(1, 5):
    attrname = "entryplot_val{}".format(x)
    getattr(self, attrname).delete(0, tk.END)

for x in range(1, 5):
    get_attr(self, "entryplot_val{}".format(x)).delete(0, tk.END)

for x in range(1, 5):
    attr_name = f'entryplot_val{x}'
    getattr(self, attr).delete(0, tk.END)