Cant create index with dataframe columns

Question

I'm trying to use dataframe columns to create an index.

#columns in file [<TICKER>,<PER>,<DATE>,<TIME>,<OPEN>,<HIGH>,<LOW>,<CLOSE>,<VOL>]
df = pd.read_csv('DSKY_210101_211106.csv', header=0, parse_dates=[2, 3])
#projection
project = df[['<DATE>', '<TIME>', '<HIGH>']]
project.set_index(['<DATE>','<TIME>'])
print(project)

But the index still the same. Why didn't columns become index ?

set_index by default creates a new df object, if you want it to change the existing one set inplace=true you can see this in the docs pandas.pydata.org/docs/reference/api/… inplacebool, default False If True, modifies the DataFrame in place (do not create a new object). — Chris Doyle
– Chris Doyle, Commented Dec 8, 2021 at 16:27
Does this answer your question? Dataframe set_index not setting — BigBen
– BigBen, Commented Dec 8, 2021 at 16:50

user17242583 · Accepted Answer · 2021-12-08 16:32:38Z

2

pandas.DataFrame.set_index() is not in-place, i.e., it creates a new dataframe and modifies that. You need to reassign to project:

project = project.set_index(['<DATE>','<TIME>'])

answered Dec 8, 2021 at 16:32

user17242583

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8 Comments

BigBen Over a year ago

This is a duplicate. There's no need to answer a question that has been already asked and answered elsewhere. Please first look for duplicates before answering questions, and vote to close as duplicate when appropriate, thanks!

user17242583 Over a year ago

Oh really? Ok, thank you for find it. I didn't know that there was. I'll save it. :)

BigBen Over a year ago

(In other words, there are many many duplicates in the pandas tag)

BigBen Over a year ago

Fair enough! My rule of thumb: if it's a basic pandas question, it's been asked (probably many times) already on this site :D

BigBen Over a year ago

Jezrael's profile has a convenient list haha

|

Learning is a mess · Accepted Answer · 2021-12-08 16:36:00Z

0

Adding to @user17242583's answer pd.Dataframe.set_index is not inplace unless specified in its arguments:

#columns in file [<TICKER>,<PER>,<DATE>,<TIME>,<OPEN>,<HIGH>,<LOW>,<CLOSE>,<VOL>]
df = pd.read_csv('DSKY_210101_211106.csv', header=0, parse_dates=[2, 3])
#projection
project = df[['<DATE>', '<TIME>', '<HIGH>']]
project.set_index(['<DATE>','<TIME>'], inplace=True)
print(project)

edited Dec 8, 2021 at 16:36

user17242583

answered Dec 8, 2021 at 16:34

Learning is a mess

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Comments

sudeep garg · Accepted Answer · 2021-12-08 17:13:11Z

-1

Please use the set_index with inplace= True

answered Dec 8, 2021 at 17:13

sudeep garg

12 bronze badges

2 Comments

BigBen Over a year ago

This adds nothing but noise to the thread, which is already a duplicate. Please don't do that.

Montresor Over a year ago

This does not add anything to the thread

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