Dataframe index (only) to CSV python

Question

I'm trying to convert some data to pandas dataframe. Somehow, the dataframe turned out to be empty. The print statement shows the following (part of it)

Empty DataFrame
Columns: []
Index: [count  "a" "33" "37" "asd7"]
Empty DataFrame
Columns: []
Index: [data  "2434" "33" "37" "[email protected]"]

I'd like to write the dataframe to a csv file. Since the dataframe is empty, can I write the indexes into a csv file like

count,data
a,2434
33,33
37,37
asd7,[email protected]

I know I can write a dataframe to csv using data.to_csv, but how do I achieve the above stated?

cd98 · Accepted Answer · 2014-11-16 23:05:55Z

2

df1 = pd.DataFrame(index=["a", "33", "37", "asd7"], )
df2 = pd.DataFrame(index=["2434", "33", "37", "[email protected]"])
df1.index.name = 'count'
df2.index.name = 'data'

You already have objects similar to df1 and df2. Just do:

df1.reset_index(inplace=True)
df2.reset_index(inplace=True)

df3 = pd.concat([df1, df2], axis=1)

gives

   count data
0   a    2434
1   33   33
2   37   37
3   asd7 [email protected]

finally:

df3.to_csv("file_name.csv")

answered Nov 16, 2014 at 23:05

cd98

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1 Comment

mrbTT Over a year ago

Not related to the question, but thanks for the df1.index.name = 'count'. Did not know you could name the index.

Anzel · Accepted Answer · 2014-11-16 21:45:50Z

1

Probably not the best approach but this normal for/loop with zip can write the csv as you asked:

df
Empty DataFrame
Columns: []
Index: [count, a, 33, 37, asd7]

df1
Empty DataFrame
Columns: []
Index: [data, 2434, 33, 37, [email protected]]

with open('combined_pd.csv', 'w') as f:
    for x,y in zip(df.index, df1.index):
        f.write(x + ',' + y +'\n')

>>>cat combined_pd.csv
count,data
a,2434
33,33
37,37
asd7,[email protected]

answered Nov 16, 2014 at 21:45

Anzel

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2 Comments

cd98 Over a year ago

Looping with dataframes will likely be very slow and is more difficult to read.

Anzel Over a year ago

@cd98, looping with dataframes of course will be slow. However, looping their indexes which are basically lists and write to file, will be much more efficient and quicker than reset_index and concat in OP use case. That said, I do like your approach to do things in pandas way :0

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