python pandas flatten a dataframe to a list

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Question :

python pandas flatten a dataframe to a list

I have a df like so:

import pandas
a=[['1/2/2014', 'a', '6', 'z1'], 
   ['1/2/2014', 'a', '3', 'z1'], 
   ['1/3/2014', 'c', '1', 'x3'],
df = pandas.DataFrame.from_records(a[1:],columns=a[0])

I want to flatten the df so it is one continuous list like so:

['1/2/2014', 'a', '6', 'z1', '1/2/2014', 'a', '3', 'z1','1/3/2014', 'c', '1', 'x3']

I can loop through the rows and extend to a list, but is a much easier way to do it?

Asked By: jason


Answer #1:

You can just use .flatten() on the DataFrame:


and you can also add .tolist() if you want the result to be a Python list.


As suggested in the comments, now .to_numpy() is recommended instead of .values.

Answer #2:

Maybe use stack?

array(['1/2/2014', 'a', '3', 'z1', '1/3/2014', 'c', '1', 'x3'], dtype=object)

(Edit: Incidentally, the DF in the Q uses the first row as labels, which is why they’re not in the output here.)

Answered By: meloncholy

Answer #3:

You can try with numpy

import numpy as np
np.reshape(df.values, (1,df.shape[0]*df.shape[1]))
Answered By: Chitrasen

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