Python: Convert two columns of dataframe into one interposed list

Question

How can I convert two columns in a dataframe into an interposed list?

ex: I want to do something like

df

             Open  Close
Date
2016-12-23  1      2
2016-12-27  3      4
2016-12-28  5      6
2016-12-29  0      -1

someFunction(df)

>>> [1, 2, 3, 4, 5, 6, 0, -1]

Closest I've found is list(zip(df.Open, df.Close) but that returns a bunch of tuples in the list like this: [(1, 2), (3, 4), (5, 6), (0, -1)]

Does this answer your question? [Pythonic way to combine two lists in an alternating fashion?](https://stackoverflow.com/questions/3678869/pythonic-way-to-combine-two-lists-in-an-alternating-fashion) — Simon Crane, Dec 25 '19 at 23:21

score 5 · Accepted Answer · answered Dec 25 '19 at 23:22

5

Try this:

df.values.flatten()                                                                                                                                                                  
# array([ 1,  2,  3,  4,  5,  6,  0, -1])

answered Dec 25 '19 at 23:22

oppressionslayer

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Ah, what if there are a bunch of other columns in between? Is there a more pythonic way than just grabbing the first 2 columns into its own DF or dropping the rest of the columns? – Michael Dec 25 '19 at 23:24
If you want, you can just pick the columns you want to flatten: df[['Open', 'Close']].values.flatten() – oppressionslayer Dec 25 '19 at 23:27
this is: `df.stack().values` – ansev Dec 25 '19 at 23:30

score 2 · Answer 2 · answered Dec 25 '19 at 23:18

2

IIUC

df.values.ravel().tolist()#df.to_numpy().ravel().tolist()

[1, 2, 3, 4, 5, 6, 0, -1]

answered Dec 25 '19 at 23:18

BENY

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may I know the reason downvote ? – BENY Dec 26 '19 at 18:03

score 2 · Answer 3 · answered Dec 25 '19 at 23:30

2

How about:

df.stack().values
#array([ 1,  2,  3,  4,  5,  6,  0, -1])

answered Dec 25 '19 at 23:30

ansev

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score 1 · Answer 4 · answered Dec 25 '19 at 23:19

1

You can obtain the values, and reshape it to a 1d array:

>>> df[['Open', 'Close']].values.reshape(-1)
array([ 1,  2,  3,  4,  5,  6,  0, -1])

or convert that to a list:

>>> list(df[['Open', 'Close']].values.reshape(-1))
[1, 2, 3, 4, 5, 6, 0, -1]

answered Dec 25 '19 at 23:19

Willem Van Onsem

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score 1 · Answer 5 · answered Dec 25 '19 at 23:19

1

You could use a list comprehension in combination with df.values:

[y for x in df.values for y in x]
[1, 2, 3, 4, 5, 6, 0, -1]

x will be an array with the rows, and y will be the values in those rows

answered Dec 25 '19 at 23:19

KenHBS

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Python: Convert two columns of dataframe into one interposed list

5 Answers5