plot时为何不显示图形？

[panzhixiong_cn]

我使用的是Canopy集成开发环境，如下代码都正常运行，但就是没有图出来。请教各位大神了？
import pandas as pd

names1980 = pd.read_csv('D:/data/names/yob1880.txt', names=['name', 'sex', 'births'])

years = range(1880, 2011)

pieces = []
columns = ['name', 'sex', 'births']

for year in years:
path = 'D:/data/names/yob%d.txt' % year
frame = pd.read_csv(path, names=columns)

frame['year'] = year
pieces.append(frame)

#将所有数据整合到单个DataFrame中
names = pd.concat(pieces, ignore_index=True)

total_births = names.pivot_table('births', index='year', columns='sex', aggfunc=sum)


total_births.plot(title='Total births by sex and year')[/code]

[secsilm]

需要用 plt.show() 来显示，前面导入 matplotlib 模块：import matplotlib.pyplot as plt