我尝试在一个csv文件中更新库存数据，在另一个csv文件中使用新行。由于我检索此数据的方式，行部分重叠。基本库存文件包含（简化示例）：
Mar 08, 2016 9692.82 9688.47 9785.05 9617.69 95.75M -0.88% Mar 07, 2016 9778.93 9764.08 9803.73 9690.00 78.15M -0.46% Mar 04, 2016 9824.17 9800.86 9899.11 9742.76 93.45M 0.74% Mar 03, 2016 9751.92 9807.06 9808.52 9709.68 85.25M -0.25% Mar 02, 2016 9776.62 9780.84 9837.11 9695.98 106.45M 0.61% Mar 01, 2016 9717.16 9482.66 9719.02 9471.09 99.54M 2.34% Feb 29, 2016 9495.40 9424.93 9498.57 9332.42 93.79M -0.19%
应使用第二个文件中的数据更新此文件：
Mar 11, 2016 9831.13 9672.05 9833.90 9642.79 118.96M 3.51% Mar 10, 2016 9498.15 9697.64 9995.84 9498.15 177.50M -2.31% Mar 09, 2016 9723.09 9700.16 9838.95 9679.19 100.90M 0.31% Mar 08, 2016 9692.82 9688.47 9785.05 9617.69 95.75M -0.88% Mar 07, 2016 9778.93 9764.08 9803.73 9690.00 78.15M -0.46%
我用来尝试实现更新的代码如下：
existingquotes = pd.read_csv(filenames_quotes[i], parse_dates=[0], infer_datetime_format=True, header=None, delimiter='\t')
newquotes = pd.read_csv(filenames_upd[i], parse_dates=[0], infer_datetime_format=True, header=None, delimiter='\t')
existingquotes.update(newquotes)
mergedquotes=existingquotes
print mergedquotes
输出如下：
0 1 2 3 4 5 6 0 2016-03-11 9831.13 9672.05 9833.90 9642.79 118.96M 3.51% 1 2016-03-10 9498.15 9697.64 9995.84 9498.15 177.50M -2.31% 2 2016-03-09 9723.09 9700.16 9838.95 9679.19 100.90M 0.31% 3 2016-03-08 9692.82 9688.47 9785.05 9617.69 95.75M -0.88% 4 2016-03-07 9778.93 9764.08 9803.73 9690.00 78.15M -0.46% 5 2016-03-01 9717.16 9482.66 9719.02 9471.09 99.54M 2.34% 6 2016-02-29 9495.40 9424.93 9498.57 9332.42 93.79M -0.19%
2016-03-01与016-03-07之间存在差距。如果我使用
existingquotes.update(newquotes), overwrite=False)
更新看起来像原始的csv。感谢任何帮助！
答案 0 :(得分：2)
您可以先将参数<div class="container">
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添加到read_csv，以便将第一列设置为index_col=[0]，然后通过两个索引的联合添加reindex并使用最后一个使用函数combine_first按Datetimeindex NaN的值填充DataFrame：
newquotes如果print existingquotes
1 2 3 4 5 6
0
2016-03-08 9692.82 9688.47 9785.05 9617.69 95.75M -0.88%
2016-03-07 9778.93 9764.08 9803.73 9690.00 78.15M -0.46%
2016-03-04 9824.17 9800.86 9899.11 9742.76 93.45M 0.74%
2016-03-03 9751.92 9807.06 9808.52 9709.68 85.25M -0.25%
2016-03-02 9776.62 9780.84 9837.11 9695.98 106.45M 0.61%
2016-03-01 9717.16 9482.66 9719.02 9471.09 99.54M 2.34%
2016-02-29 9495.40 9424.93 9498.57 9332.42 93.79M -0.19%
print newquotes
1 2 3 4 5 6
0
2016-03-11 9831.13 9672.05 9833.90 9642.79 118.96M 3.51%
2016-03-10 9498.15 9697.64 9995.84 9498.15 177.50M -2.31%
2016-03-09 9723.09 9700.16 9838.95 9679.19 100.90M 0.31%
2016-03-08 9692.82 9688.47 9785.05 9617.69 95.75M -0.88%
2016-03-07 9778.93 9764.08 9803.73 9690.00 78.15M -0.46%
existingquotes = existingquotes.reindex(existingquotes.index.union(newquotes.index))
print existingquotes
1 2 3 4 5 6
0
2016-02-29 9495.40 9424.93 9498.57 9332.42 93.79M -0.19%
2016-03-01 9717.16 9482.66 9719.02 9471.09 99.54M 2.34%
2016-03-02 9776.62 9780.84 9837.11 9695.98 106.45M 0.61%
2016-03-03 9751.92 9807.06 9808.52 9709.68 85.25M -0.25%
2016-03-04 9824.17 9800.86 9899.11 9742.76 93.45M 0.74%
2016-03-07 9778.93 9764.08 9803.73 9690.00 78.15M -0.46%
2016-03-08 9692.82 9688.47 9785.05 9617.69 95.75M -0.88%
2016-03-09 NaN NaN NaN NaN NaN NaN
2016-03-10 NaN NaN NaN NaN NaN NaN
2016-03-11 NaN NaN NaN NaN NaN NaN
中的重叠值不同，您可以添加：
DataFrames但是这个样本是相同的，所以可以省略。
existingquotes.loc[existingquotes.index.intersection(newquotes.index),:] = np.nan
相反print existingquotes.combine_first(newquotes)
1 2 3 4 5 6
0
2016-02-29 9495.40 9424.93 9498.57 9332.42 93.79M -0.19%
2016-03-01 9717.16 9482.66 9719.02 9471.09 99.54M 2.34%
2016-03-02 9776.62 9780.84 9837.11 9695.98 106.45M 0.61%
2016-03-03 9751.92 9807.06 9808.52 9709.68 85.25M -0.25%
2016-03-04 9824.17 9800.86 9899.11 9742.76 93.45M 0.74%
2016-03-07 9778.93 9764.08 9803.73 9690.00 78.15M -0.46%
2016-03-08 9692.82 9688.47 9785.05 9617.69 95.75M -0.88%
2016-03-09 9723.09 9700.16 9838.95 9679.19 100.90M 0.31%
2016-03-10 9498.15 9697.64 9995.84 9498.15 177.50M -2.31%
2016-03-11 9831.13 9672.05 9833.90 9642.79 118.96M 3.51%
您可以使用fillna：
combine_first答案 1 :(得分：0)
谢谢大家，它就像一个魅力。最终代码如下所示：
existingquotes = pd.read_csv(filenames_quotes[i], index_col=[0], parse_dates=[0], infer_datetime_format=True, header=None, delimiter='\t')
newquotes = pd.read_csv(filenames_upd[i], index_col=[0], parse_dates=[0], infer_datetime_format=True, header=None, delimiter='\t')
existingquotes = existingquotes.reindex(existingquotes.index.union(newquotes.index))
existingquotes = existingquotes.fillna(newquotes)
print mergedquotes
并导致预期结果（与jezrael发布的相同）