请问我按照书上原封不动写的，结果提示出错，这是什么原因呢？

梦想在峥嵘岁月

import math
import matplotlib.pyplot as plt
import numpy as np
t=np.arange(0,2.5,0.1)
y1=map(math.sin,math.pi*t)
y2=map(math.sin,math.pi*t+math.pi/4)
y3=map(math.sin,math.pi*t-math.pi/4)
plt.plot(t,y1,'b*',t,y2,'g^',t,y3,'ys')




Traceback (most recent call last):

  File "<ipython-input-17-fee227002740>", line 9, in <module>
    plt.plot(t,y1,'b*',t,y2,'g^',t,y3,'ys')

  File "D:\Users\yushui\Anaconda3\lib\site-packages\matplotlib\pyplot.py", line 2813, in plot
    is not None else {}), **kwargs)

  File "D:\Users\yushui\Anaconda3\lib\site-packages\matplotlib\__init__.py", line 1810, in inner
    return func(ax, *args, **kwargs)

  File "D:\Users\yushui\Anaconda3\lib\site-packages\matplotlib\axes\_axes.py", line 1611, in plot
    for line in self._get_lines(*args, **kwargs):

  File "D:\Users\yushui\Anaconda3\lib\site-packages\matplotlib\axes\_base.py", line 393, in _grab_next_args
    yield from self._plot_args(this, kwargs)

  File "D:\Users\yushui\Anaconda3\lib\site-packages\matplotlib\axes\_base.py", line 370, in _plot_args
    x, y = self._xy_from_xy(x, y)

  File "D:\Users\yushui\Anaconda3\lib\site-packages\matplotlib\axes\_base.py", line 205, in _xy_from_xy
    by = self.axes.yaxis.update_units(y)

  File "D:\Users\yushui\Anaconda3\lib\site-packages\matplotlib\axis.py", line 1467, in update_units
    converter = munits.registry.get_converter(data)

  File "D:\Users\yushui\Anaconda3\lib\site-packages\matplotlib\units.py", line 181, in get_converter
    converter = self.get_converter(next_item)

  File "D:\Users\yushui\Anaconda3\lib\site-packages\matplotlib\units.py", line 187, in get_converter
    thisx = safe_first_element(x)

  File "D:\Users\yushui\Anaconda3\lib\site-packages\matplotlib\cbook\__init__.py", line 1635, in safe_first_element
    raise RuntimeError("matplotlib does not support generators "

RuntimeError: matplotlib does not support generators as input

梦想在峥嵘岁月

知道解决的方法了
import math
import matplotlib.pyplot as plt
import numpy as np
t=np.arange(0,2.5,0.1)
y1=list（map(math.sin,math.pi*t)）
y2=list（map(math.sin,math.pi*t+math.pi/4)）
y3=list（map(math.sin,math.pi*t-math.pi/4)）
plt.plot(t,y1,'b*',t,y2,'g^',t,y3,'ys')
用python3 map不返回列表，而是返回一个生成器。