Convert list to dataframe by adding list values to df within for loop pandas

Question

I have a simple list

Code to retrieve i, v list:

 for i, v in enumerate(list_name_1):
    print(i, v)

Output

I wish to store all these in a dataframe.

The problem is I am doing lot of calculations on list_name_1 within the for loop, hence I need to catch i and v values in the for loop only. So I cant do a simple df=pd.DataFrame(list_name_1) for e.g.

I will need to do something like below:

df = []
 for i, v in enumerate(list_name_1):
        print(i, v)
        some code to add i,v iteratively in columns i and v of df

You say "...of a dataframe with column names i and v", but in your example, all entries in the list_name_1 are unique, so the DataFrame should have very many columns, and very few rows? — Marcus
– Marcus, Commented Oct 19, 2020 at 6:39
Hi In list we only have 2 types of values i and v. I want to convert these to a dataframe with 2 columns i and v. So df will have 2 columns and many rows — noob
– noob, Commented Oct 19, 2020 at 6:40
Bascially list is feature importance. i is feature number, v is feature's value.. So I want to get this data in a df and be able to do some operations on it in df format — noob
– noob, Commented Oct 19, 2020 at 6:41
I've added an answer that I think does what you want. Let me know if there are any unclarities — Marcus
– Marcus, Commented Oct 19, 2020 at 6:48

Marcus · Accepted Answer · 2020-10-19 06:45:28Z

2

An idea is to create two lists, one which stores the calculated values of i, and one for v. So:

i_values = []
v_values = []
for i, v in enumerate(list_name_1):
    print(i, v)
    # Make calculations for i and v
    i_values.extend([calculated_i])
    v_values.extend([calculated_v])

df = pd.DataFrame(data={"i": i_values, "v": v_values})

answered Oct 19, 2020 at 6:45

Marcus

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3 Comments

noob Over a year ago

NameError: name 'calculated_i' is not defined error. I am getting this error

noob Over a year ago

Works well, thanks. instead of calculated_i replaced with i

Marcus Over a year ago

I was under the impression that you wanted to make calculations in the loop, that was why I called them calculated_i. But hey, if it works and you're satisfied its all good!

Evandro Lippert · Accepted Answer · 2020-10-19 07:05:10Z

1

I think you can do that:

for i, v in enumerate(list_name_1):
    diction = {'i': i, 'v': v}
    df = df.append(diction, ignore_index=True)

I don't know how you are doing the calculation, but I think it is a good way to catch all values.

answered Oct 19, 2020 at 7:05

Evandro Lippert

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1 Comment

Marcus Over a year ago

If list_name_1 is very long, the loop will become very slow and performance will deteriorate since df.append() is generally bad practice in loops. You can read more about why here: stackoverflow.com/questions/27929472/…

OmkarKhilari · Accepted Answer · 2020-10-19 07:01:59Z

-2

I think you should use predifined syntax for this.Using for loops is really long way.

import pandas as pd

L = ["This","Is","A","List"]
M = ["This","Is","Also","List"]
#create new dataframe
df = pd.DataFrame({'col':L,'col2':M})
print (df)


           col  col2
       0  This  This
       1    Is    Is
       2     A  Also
       3  List  List

edited Oct 19, 2020 at 7:01

answered Oct 19, 2020 at 6:46

OmkarKhilari

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