Create single row python pandas dataframe

Question

I want to create a python pandas DataFrame with a single row, to use further pandas functionality like dumping to *.csv.

I have seen code like the following being used, but I only end up with the column structure, but empty data

import pandas as pd

df = pd.DataFrame()
df['A'] = 1
df['B'] = 1.23
df['C'] = "Hello"
df.columns = [['A','B','C']]

print df

Empty DataFrame
Columns: [A, B, C]
Index: []

While I know there are other ways to do it (like from a dictionary), I want to understand why this piece of code is not working for me!? Is this a version issue? (using pandas==0.19.2)

You need two wrap the first one in brackets: df['A'] = [1] — user2285236
– user2285236, Commented Aug 4, 2017 at 10:22
alternatively, if you add df = pd.DataFrame(index=[0]) - then your code should work properly — MaxU - stand with Ukraine
– MaxU - stand with Ukraine, Commented Aug 4, 2017 at 10:28
@MaxU this indeed makes the above code runnable as it is. But the code as posted above is not runnable itself (or at least creates empty dataframs), is this correct? So the above code can be considered as buggy!? — HeXor
– HeXor, Commented Aug 7, 2017 at 9:33
@HeXor, it depends on the definition of "buggy code"... Pandas allows us to do things in many different ways. IMO the most idiomatic way of creating DFs is to collect the data and then create DF at once compared to adding single rows, which is usually pretty inefficient... — MaxU - stand with Ukraine
– MaxU - stand with Ukraine, Commented Aug 7, 2017 at 9:44

MaxU - stand with Ukraine · Accepted Answer · 2017-08-04 10:22:23Z

81

In [399]: df = pd.DataFrame(columns=list('ABC'))

In [400]: df.loc[0] = [1,1.23,'Hello']

In [401]: df
Out[401]:
   A     B      C
0  1  1.23  Hello

or:

In [395]: df = pd.DataFrame([[1,1.23,'Hello']], columns=list('ABC'))

In [396]: df
Out[396]:
   A     B      C
0  1  1.23  Hello

answered Aug 4, 2017 at 10:22

MaxU - stand with Ukraine

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Comments

James Hirschorn · Accepted Answer · 2022-07-31 17:23:46Z

7

If you are creating the DataFrame from a dict you can do the following:

>>> data = dict(A=1, B=1.23, C='Hello')
>>> df = pd.DataFrame(data, index=[0])
>>> df
   A     B      C
0  1  1.23  Hello

answered Jul 31, 2022 at 17:23

James Hirschorn

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mas192 · Accepted Answer · 2022-03-16 17:41:48Z

0

I know this is an old post, but based on this explanation in this post Creating an empty Pandas DataFrame, then filling it?

We should not be doing dataframe adding. I am asking this because I am doing something similar but I opted for the solution in the post I shared over this one.

answered Mar 16, 2022 at 17:41

mas192

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AstroFloyd · Accepted Answer · 2023-09-09 05:52:04Z

0

I ended here because I want to create a single-row Pandas DataFrame from a numerical list (or NumPy array) but got a df with a single column. @ayhan's first comment was what I needed:

  import pandas as pd
  lst = [1,2,3]
  df = pd.DataFrame(lst)    # df with a single column
  df = pd.DataFrame([lst])  # df with a single row

answered Sep 9, 2023 at 5:52

AstroFloyd

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