问题
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.
回答1:
Try: grouped.get_group('foo'), that is what you need.
回答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 =
来源：https://stackoverflow.com/questions/22702486/pandas-how-to-get-a-particular-group-after-groupby