converting rows of a single dataFrame column into a single list in python

Question

I have a pandas Series and I would like to covert all the rows of my series into a single list. I have:

list1=Series([89.34,88.52,104.19,186.84,198.15,208.88]). Then I have a function which i call:
func(list1)
def func(list1):
   list1=list1.values.tolist()
   print(list1)

the printed result is :

[[89.34], [88.52], [104.19], [186.84], [198.15], [208.88]]

but I would like to have : [89.34,88.52,104.19,186.84,198.15,208.88]

any help. I am using python 2.7

You should not use list as a variable name because it a globally accessible data structure. — Ray
– Ray, Commented Aug 14, 2015 at 20:38
I couldn't reproduce the problem you had. Could you add python version, pandas version and what OS you use? — tmrlvi
– tmrlvi, Commented Aug 14, 2015 at 20:53
Yeah, I don't see how that code would give that result. If you had a DataFrame, and then called .values.tolist(), you'd get a list of lists, but if you have a Series, you should simply get a list. — DSM
– DSM, Commented Aug 14, 2015 at 20:55

Ray · Accepted Answer · 2015-08-14 20:58:35Z

1

Easiest way would be to access the values property of the Series object, like you have in your example.

> from pandas import Series
> a_series = Series([89.34,88.52,104.19,186.84,198.15,208.88])
> print(a_series.values.tolist())
[89.34, 88.52, 104.19, 186.84, 198.15, 208.88]

Accessing more than one elements in the list at the same time:

> counter = 0
> a_list = a_series.values.tolist()
> while(counter < len(a_list)):
..    if((counter+1) < len(a_list)):
..        print(a_list[counter] == a_list[counter+1])
..    counter+=1
False
False
False
False
False

edited Aug 14, 2015 at 20:58

answered Aug 14, 2015 at 20:47

Ray

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5 Comments

user3841581 Over a year ago

Thanks Ray,the problem with this is that i would like to iterate through that list starting at the second index; that is your elem+1 and compare it with elem

tmrlvi Over a year ago

Then you don't need to you a list. You can do more efficiently with pandas objects. Use b_series = a_series.shift(-1) to create series that has the same indexes, only the data is shifted. Then you can use for example a_series - b_series to get the difference

Ray Over a year ago

I added a way to compare elements to previous elements. If I am mistaken please let me know. Any logic requirements (like comparing elem+1 to elem) should be in your question so there is no confusion.

user3841581 Over a year ago

@Ray i have a curious question though; assuming it was a DataFrame and that i am passing just one column; how will it work?

Ray Over a year ago

You would have to add another loop inside the while loop since you would then be iterating over "columns" and "rows". Unless pandas has a built-in that makes this easier. I'm not that familiar with pandas to be honest. The docs have a few interesting methods mentioned (like DataFrame.applymap) that may work.

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