将 pandas 数据框与重叠的列/行组合 [英] Combining pandas data frames with overlapping columns / rows

问题描述

我正在寻找一种有效的方式来组合100个熊猫数据框，这些数据框代表信息点的网格.这些数据帧的每个点都是唯一的，并且不与另一个数据帧的点重叠，但是它们确实在更大的拼凑空间中共享列和行. 即

I am looking for an efficient way to combine 100 pandas data frames, which represent a grid of information points. Each of these data frames' points is unique, and does not overlap points represented by another, but they do share columns and rows over a larger patchwork space. i.e.

     1    2    3        4    5    6        7    8    9
A    df1, df1, df1,     df2, df2, df2,     df3, df3, df3
B    df1, df1, df1,     df2, df2, df2,     df3, df3, df3
C    df1, df1, df1,     df2, df2, df2,     df3, df3, df3

D    df4, df4, df4,     df5, df5, df5,     etc, etc, etc
E    df4, df4, df4,     df5, df5, df5,     etc, etc, etc
F    df4, df4, df4,     df5, df5, df5,     etc, etc, etc

Pandas的连接仅在列或行轴上组合，而不能在两者之间组合.因此，我一直在尝试增加数据帧的数量，并使用df1.combine_first(df2)方法(无限重复).

Pandas' concatenate only combines over either the columns or the row axis, but not both. So I've been trying to increment over the data frames and using the df1.combine_first(df2) method (repeat ad infinitum).

这是最好的方法，还是我应该意识到的另一种更有效的方法?

Is this the best way to proceed, or is there another more efficient method that I should be aware of?

推荐答案

这里基于非重叠数据点并假设非常规则的数据(在这种情况下为3x3)，快速地从便利性角度和效率角度进行了猜测. >

Here's a quick guess at both the convenience and efficiency angles, based on non-overlapping datapoints and assuming very regular data (everything 3x3 in this case).

df1=pd.DataFrame( np.random.randn(3,3), index=list('ABC'), columns=list('123') )
df2=pd.DataFrame( np.random.randn(3,3), index=list('DEF'), columns=list('123') )
df3=pd.DataFrame( np.random.randn(3,3), index=list('ABC'), columns=list('456') )
df4=pd.DataFrame( np.random.randn(3,3), index=list('DEF'), columns=list('456') )

combine_first方式的优点是，您可以仅将列表中的所有内容转储而不用担心顺序:

The combine_first way has the advantage that you can just dump everything in a list without worrying about the order:

%%timeit
comb_df = pd.DataFrame()
for df in [df1,df2,df3,df4]:  
    comb_df = comb_df.combine_first( df )

100 loops, best of 3: 8.92 ms per loop

concat方法要求您按特定顺序对事物进行分组，但速度要快两倍以上:

The concat way requires you to group things in a specific order, but is more than twice as fast:

%%timeit
df5 = pd.concat( [df1,df2], axis=0 )
df6 = pd.concat( [df3,df4], axis=0 )
df7 = pd.concat( [df5,df6], axis=1 )

100 loops, best of 3: 3.84 ms per loop

快速检查两种方法是否相同:

Quick check that both ways work the same:

all( comb_df == df7 )
True

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