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分享DataFrame筛选后返回的是一个新拷贝？不能返回引用吗？
求教，我希望修改df4(筛选后得到的DataFrame)，修改结果反映到原df1上，没有简单办法吗？
df1=pd.DataFrame(np.arange(16).reshape((4,4)),index=['a','b','c','d'],columns=['one','two','three','four'])
print df1
df2 = df1.copy()
df3 = df1
df4 = df1[df1['three'] > 2] #经过过滤df4已经是一个新的DataFrame对象，对它的修改不会反映到df1上
df2['one'][1] = 222
df3['one'][1] = 333
df4['one'][1] = 444
print df1
print df2
print df3
print df4
df1=pd.DataFrame(np.arange(16).reshape((4,4)),index=['a','b','c','d'],columns=['one','two','three','four'])
print df1
df2 = df1.copy()
df3 = df1
df4 = df1[df1['three'] > 2] #经过过滤df4已经是一个新的DataFrame对象，对它的修改不会反映到df1上
df2['one'][1] = 222
df3['one'][1] = 333
df4['one'][1] = 444
print df1
print df2
print df3
print df4
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acneyang 2018-01-11
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acneyang 2018-01-10
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运行结果
one two three four
a 0 1 2 3
b 4 5 6 7
c 8 9 10 11
d 12 13 14 15
one two three four
a 0 1 2 3
b 333 5 6 7
c 8 9 10 11
d 12 13 14 15
one two three four
a 0 1 2 3
b 222 5 6 7
c 8 9 10 11
d 12 13 14 15
one two three four
a 0 1 2 3
b 333 5 6 7
c 8 9 10 11
d 12 13 14 15
one two three four
b 4 5 6 7
c 444 9 10 11
d 12 13 14 15
