Pandas: how to get a particular group after groupby?

Question

I want to group a dataframe by a column, called 'A', and inspect a particular group.

grouped = df.groupby('A', sort=False)

However, I don't know how to access a group, for example, I expect that

grouped.first() 

would give me the first group

Or

grouped['foo'] 

would give me the group where A=='foo'.

However, Pandas doesn't work like that.

I couldn't find a similar example online.

Solution 1

Try: grouped.get_group('foo'), that is what you need.

Solution 2

from io import StringIO # from StringIO... if python 2.X
import pandas
data = pandas.read_csv(StringIO("""\
area,core,stratum,conc,qual
A,1,a,8.40,=
A,1,b,3.65,=
A,2,a,10.00,=
A,2,b,4.00,ND
A,3,a,6.64,=
A,3,b,4.96,=
"""), index_col=[0,1,2])

groups = data.groupby(level=['area', 'stratum'])
groups.get_group(('A', 'a')) # make sure it's a tuple

                    conc qual
area core stratum            
A    1    a         8.40    =
     2    a        10.00    =
     3    a         6.64    =