我有一个Pandas数据帧,如下所示,有多个列,并想获得列的总数,MyColumn。
打印df
X MyColumn Y Z
0 A 84 13.0 69.0
1 B 76 77.0 127.0
2 C 28 69.0 16.0
3 D 28 28.0 31.0
4 E 19 20.0 85.0
5 F 84 193.0 70.0
我的尝试:
我已经尝试使用groupby和.sum()获得列的和:
Total = df.groupby['MyColumn'].sum()
print Total
这将导致以下错误:
TypeError: 'instancemethod' object has no attribute '__getitem__'
预期的输出
我原本期望输出如下:
319
或者,我想用一个名为TOTAL的新行编辑df,其中包含总数:
X MyColumn Y Z
0 A 84 13.0 69.0
1 B 76 77.0 127.0
2 C 28 69.0 16.0
3 D 28 28.0 31.0
4 E 19 20.0 85.0
5 F 84 193.0 70.0
TOTAL 319
另一种选择是:
df.loc["Total", "MyColumn"] = df.MyColumn.sum()
# X MyColumn Y Z
#0 A 84.0 13.0 69.0
#1 B 76.0 77.0 127.0
#2 C 28.0 69.0 16.0
#3 D 28.0 28.0 31.0
#4 E 19.0 20.0 85.0
#5 F 84.0 193.0 70.0
#Total NaN 319.0 NaN NaN
你也可以使用append()方法:
df.append(pd.DataFrame(df.MyColumn.sum(), index = ["Total"], columns=["MyColumn"]))
更新:
如果您需要为所有数字列附加sum,您可以执行以下操作之一:
使用append以函数式的方式完成此操作(不会改变原始数据帧):
# select numeric columns and calculate the sums
sums = df.select_dtypes(pd.np.number).sum().rename('total')
# append sums to the data frame
df.append(sums)
# X MyColumn Y Z
#0 A 84.0 13.0 69.0
#1 B 76.0 77.0 127.0
#2 C 28.0 69.0 16.0
#3 D 28.0 28.0 31.0
#4 E 19.0 20.0 85.0
#5 F 84.0 193.0 70.0
#total NaN 319.0 400.0 398.0
使用loc改变数据帧的位置:
df.loc['total'] = df.select_dtypes(pd.np.number).sum()
df
# X MyColumn Y Z
#0 A 84.0 13.0 69.0
#1 B 76.0 77.0 127.0
#2 C 28.0 69.0 16.0
#3 D 28.0 28.0 31.0
#4 E 19.0 20.0 85.0
#5 F 84.0 193.0 70.0
#total NaN 638.0 800.0 796.0
你应该使用sum:
Total = df['MyColumn'].sum()
print(Total)
319
然后你使用loc与Series,在这种情况下,索引应该设置为与你需要求和的特定列相同:
df.loc['Total'] = pd.Series(df['MyColumn'].sum(), index=['MyColumn'])
print(df)
X MyColumn Y Z
0 A 84.0 13.0 69.0
1 B 76.0 77.0 127.0
2 C 28.0 69.0 16.0
3 D 28.0 28.0 31.0
4 E 19.0 20.0 85.0
5 F 84.0 193.0 70.0
Total NaN 319.0 NaN NaN
因为如果你传递标量,所有行的值都将被填充:
df.loc['Total'] = df['MyColumn'].sum()
print(df)
X MyColumn Y Z
0 A 84 13.0 69.0
1 B 76 77.0 127.0
2 C 28 69.0 16.0
3 D 28 28.0 31.0
4 E 19 20.0 85.0
5 F 84 193.0 70.0
Total 319 319 319.0 319.0
at和ix还有两种解决方案,具体应用如下:
df.at['Total', 'MyColumn'] = df['MyColumn'].sum()
print(df)
X MyColumn Y Z
0 A 84.0 13.0 69.0
1 B 76.0 77.0 127.0
2 C 28.0 69.0 16.0
3 D 28.0 28.0 31.0
4 E 19.0 20.0 85.0
5 F 84.0 193.0 70.0
Total NaN 319.0 NaN NaN
df.ix['Total', 'MyColumn'] = df['MyColumn'].sum()
print(df)
X MyColumn Y Z
0 A 84.0 13.0 69.0
1 B 76.0 77.0 127.0
2 C 28.0 69.0 16.0
3 D 28.0 28.0 31.0
4 E 19.0 20.0 85.0
5 F 84.0 193.0 70.0
Total NaN 319.0 NaN NaN
注意:从Pandas v0.20开始,ix已弃用。使用loc或iloc代替。