8
问题:
我想两个相对较小的数据集在一起,但合并提出了一个MemoryError
。我有两个国家贸易数据汇总数据集,我试图在关键年份和国家进行合并,因此数据需要特殊放置。这不幸的是使用了concat
,并且在这个问题的答案中看到了它的性能好处:MemoryError on large merges with pandas in Python。熊猫合并错误:的MemoryError
这里的设置:
尝试的合并:
df = merge(df, i, left_on=['year', 'ComTrade_CC'], right_on=["Year","Partner Code"])
基本数据结构:
我:
Year Reporter_Code Trade_Flow_Code Partner_Code Classification Commodity Code Quantity Unit Code Supplementary Quantity Netweight (kg) Value Estimation Code
0 2003 381 2 36 H2 070951 8 1274 1274 13810 0
1 2003 381 2 36 H2 070930 8 17150 17150 30626 0
2 2003 381 2 36 H2 0709 8 20493 20493 635840 0
3 2003 381 1 36 H2 0507 8 5200 5200 27619 0
4 2003 381 1 36 H2 050400 8 56439 56439 683104 0
DF:
mporter cod CC ComTrade_CC Distance_miles
0 110 215 215 757 428.989
1 110 215 215 757 428.989
2 110 215 215 757 428.989
3 110 215 215 757 428.989
4 110 215 215 757 428.989
错误回溯:
MemoryError Traceback (most recent call last)
<ipython-input-10-8d6e9fb45de6> in <module>()
1 for i in c_list:
----> 2 df = merge(df, i, left_on=['year', 'ComTrade_CC'], right_on=["Year","Partner Code"])
/usr/local/lib/python2.7/dist-packages/pandas-0.12.0rc1_309_g9fc8636-py2.7-linux-x86_64.egg/pandas/tools/merge.pyc in merge(left, right, how, on, left_on, right_on, left_index, right_index, sort, suffixes, copy)
36 right_index=right_index, sort=sort, suffixes=suffixes,
37 copy=copy)
---> 38 return op.get_result()
39 if __debug__:
40 merge.__doc__ = _merge_doc % '\nleft : DataFrame'
/usr/local/lib/python2.7/dist-packages/pandas-0.12.0rc1_309_g9fc8636-py2.7-linux-x86_64.egg/pandas/tools/merge.pyc in get_result(self)
193 copy=self.copy)
194
--> 195 result_data = join_op.get_result()
196 result = DataFrame(result_data)
197
/usr/local/lib/python2.7/dist-packages/pandas-0.12.0rc1_309_g9fc8636-py2.7-linux-x86_64.egg/pandas/tools/merge.pyc in get_result(self)
693 if klass in mapping:
694 klass_blocks.extend((unit, b) for b in mapping[klass])
--> 695 res_blk = self._get_merged_block(klass_blocks)
696
697 # if we have a unique result index, need to clear the _ref_locs
/usr/local/lib/python2.7/dist-packages/pandas-0.12.0rc1_309_g9fc8636-py2.7-linux-x86_64.egg/pandas/tools/merge.pyc in _get_merged_block(self, to_merge)
706 def _get_merged_block(self, to_merge):
707 if len(to_merge) > 1:
--> 708 return self._merge_blocks(to_merge)
709 else:
710 unit, block = to_merge[0]
/usr/local/lib/python2.7/dist-packages/pandas-0.12.0rc1_309_g9fc8636-py2.7-linux-x86_64.egg/pandas/tools/merge.pyc in _merge_blocks(self, merge_chunks)
728 # Should use Fortran order??
729 block_dtype = _get_block_dtype([x[1] for x in merge_chunks])
--> 730 out = np.empty(out_shape, dtype=block_dtype)
731
732 sofar = 0
MemoryError:
感谢您的想法!
你似乎在'df'中有重复项当你删除重复项然后合并时会发生什么? 'df.drop_duplicates(inplace = True)' – EdChum
它们实际上并不重复。 df实际上包含93列,每个观察对于年度和贸易伙伴都是独特的。我只想把一小部分数据放在SO上以避免混淆。感谢这个想法艰难!此外,合并似乎没有形式缺乏记忆。当我进行合并时,我没有使用超过50%的记忆。 – agconti
不用担心,另一件需要检查的问题是,如果你在任何合并列中有任何NaN(null)值,那么你应该怎么做,但如果你有任何 – EdChum