问使用python上的输入将y图添加到matlib

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# Program for radioactive isotope graph

from numpy import array, empty
import numpy as np
import math                          
from math import *
import matplotlib.pyplot as plt

#gathering user data on isotope name, half life, mass and time elapsed.

while True:
    isotope = input("\nWhat is the name of your isotope? If you would like to end the program type 'stop'.")
    if isotope == "stop":
        break
    else:
        half_life = input("\nWhat is the half life of your isotope (in seconds)?")
        mass = input("\nWhat is the amount of isotope you have (in grams)?")
        time = input("\nHow long has time elapsed (in seconds)?")

        #float user integers

        half_life = float (half_life)
        mass = float (mass)
        time = float (time)

        #Calculates amount of isotope remaining.

        time_life = time/half_life

        P_over_PO = 0.5**time_life

        isotope_remain = P_over_PO*mass

        print "\nThe amount of", isotope, "that remains after the elapsed time is:", isotope_remain, "grams."

        #Calculates initial mass of isotope so after 30 seconds, 5g are left

        half_life_5grams = 30/half_life

        P_over_PO_5grams = 0.5**half_life_5grams

        initial_mass = 5/P_over_PO_5grams

        print "\nThe initial mass of", isotope, "needs to be", initial_mass, "grams to ensure that after a thirty second half life 5 g are left."

        #Creating a graph with user data

        #Creating variables for elements to be put into arrays

        graph_time = 0

        user_data = 0

        graph_mass = list()

        while user_data < 10:

          isotope_half_life = mass * exp(-log(2)*(time/half_life))

          graph_mass.append(isotope_half_life)

          graph_time = graph_time + 1

          user_data = user_data + 1

          y_cooridinates = array(graph_mass, float)

          x=np.linspace(0,10,10) 
          print "x =", x

          y=np.array(y_cooridinates,float) 
          print "y=", y

          plt.plot (x, y) 
          plt.title ('A graph showing the amount of isotope remaining as a function of elapsed time')  
          plt.xlabel ("Time/seconds") 
          plt.ylabel ("Amount of isotope/grams") 
          plt.show () 
        break