根据两列匹配来自两个csv文件的数据，并使用选定的列创建一个新的csv文件

Question

I have two csv files.

one.csv:

1, 12.1455675, -13.1287564, 23, 9, 4.5, 4
2, 12.5934593, -13.0856385, 14, 5, 9.7, 6
3, 12.0496204, -13.8938582, 14, 6, 3.4, 9
4, 12.1456084, -12.1939589, 45, 2, 3.4, 8

two.csv:

9, 12.0496, -13.8939, .3, 55
3, 12.1456, -13.1288, 3.4, 9

What I want to do is match the two csv files based on columns one and two. I want another csv file that has the matched columns 1 and 2, but also includes the corresponding 3rd column values from two.csv and 6th column values from one.csv. Like this:

12.0496, -13.8939, 55, 3.4
12.1456, -12.1288, 9, 4.5

I am unsure how to go about this especially when some of the values in two.csv are rounded.

Any help is greatly appreciated!

Answer 1

You could use pandas ' io to read/write csv files and its database-style joining/merging capabilities to merge the files:

import pandas as pd

normalize = lambda x: "%.4f" % float(x) # round
df = pd.read_csv("one.csv", index_col=(0,1), usecols=(1, 2, 5),
                 header=None, converters=dict.fromkeys([1,2], normalize))
df2 = pd.read_csv("two.csv", index_col=(0,1), usecols=(1, 2, 4),
                  header=None, converters=dict.fromkeys([1,2], normalize))
result = df.join(df2, how='inner')
result.to_csv("output.csv", header=None) # write as csv

Result

12.0496,-13.8939,3.4,55
12.1456,-13.1288,4.5,9

Answer 2

This is a quite common question on SO.

As of myself, same answer: for a medium-term solution, import in a DB, then perform a query using a JOIN ...

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Try a search: https://stackoverflow.com/search?q=combining+csv+python