Extract a column from a DataFrame

Question

Just a basic question but which block me a lot. How can we extract a column from a DataFrame and have a DataFrame as output ?

Suppose that we have :

>>> dfM
<class 'pandas.core.frame.DataFrame'>
DatetimeIndex: 17544 entries, 2015-01-01 00:00:00 to 2016-12-31 23:00:00
Data columns (total 23 columns):
T1       17544  non-null values
T2       17544  non-null values

>>> df = dfM['T1']

Here df is not a DataFrame. I found a subterfuge by copy the DataFrame and del all columns but it's very time consumming.

Alexis

David Robinson · Accepted Answer · 2014-03-23 16:00:17Z

1

You can use [[]] instead of []:

df = dfM[['T1']]

For example:

from pandas import DataFrame
df = DataFrame(dict(a=range(10), b=range(10)))

type(df['b'])
# <class 'pandas.core.series.Series'>
type(df[['b']])
# <class 'pandas.core.frame.DataFrame'>

This works because it is passing a list of 1 (['b']) to the column subset operator.

answered Mar 23, 2014 at 16:00

David Robinson

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1 Comment

Alexis G Over a year ago

Very well ! Thank you.

aha · Accepted Answer · 2014-03-23 15:57:40Z

0

One solution is to create a DataFrame with the column you want and the original index:

df = pandas.DataFrame(dfM.T1, index = dfM.index)

answered Mar 23, 2014 at 15:57

aha

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