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dataframe pandas python

How to split a column into two columns?

发布于 2020-03-31 23:00:52

I have a data frame with one column and I'd like to split it into two columns, with one column header as 'fips' and the other 'row'

My dataframe df looks like this:

          row
0    00000 UNITED STATES
1    01000 ALABAMA
2    01001 Autauga County, AL
3    01003 Baldwin County, AL
4    01005 Barbour County, AL

I do not know how to use df.row.str[:] to achieve my goal of splitting the row cell. I can use df['fips'] = hello to add a new column and populate it with hello. Any ideas? 

         fips       row
0    00000 UNITED STATES
1    01000 ALABAMA 
2    01001 Autauga County, AL
3    01003 Baldwin County, AL
4    01005 Barbour County, AL
Questioner
a k
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13.3k 2014-05-05 18:31

There might be a better way, but this here's one approach:

In [34]: import pandas as pd

In [35]: df
Out[35]: 
                        row
0       00000 UNITED STATES
1             01000 ALABAMA
2  01001 Autauga County, AL
3  01003 Baldwin County, AL
4  01005 Barbour County, AL

In [36]: df = pd.DataFrame(df.row.str.split(' ',1).tolist(),
                                   columns = ['flips','row'])

In [37]: df
Out[37]: 
   flips                 row
0  00000       UNITED STATES
1  01000             ALABAMA
2  01001  Autauga County, AL
3  01003  Baldwin County, AL
4  01005  Barbour County, AL
Crashthatch 2013-03-27 22:59:17

Be aware that .tolist() will remove any indexes you had, so your new Dataframe will be reindexed from 0 (It doesn't matter in your specific case).

root 2013-03-27 23:07:50

@Crashthatch -- then again you can just add index = df.index and you are good.

Nisba 2018-10-30 17:02:32

what if one cell can't be split?

techkuz 2019-06-13 14:05:51

AttributeError: 'DataFrame' object has no attribute 'row'

Nerxis 2019-12-18 16:07:57

@Nisba: If any cell can't be split (e.g. string doesn't contain any space for this case) it will still work but one part of the split will be empty. Other situations will happen in case you have mixed types in the column with at least one cell containing any number type. Then the split method returns NaN and the tolist method will return this value as is (NaN) which will result in ValueError (to overcome this issue you can cast it to string type before splitting). I recommend you to try it on your own it's the best way of learning :-)

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