python agg函数_python pandas自定义agg函数

Dataframe:

one two

a 1 x

b 1 y

c 2 y

d 2 z

e 3 z

grp = DataFrame.groupby('one')

grp.agg(lambda x: ???) #or equivalent function

Desired output from grp.agg:

one two

1 x|y

2 y|z

3 z

My agg function before integrating dataframes was "|".join(sorted(set(x))). Ideally I want to have any number of columns in the group and agg returns the "|".join(sorted(set()) for each column item like two above. I also tried np.char.join().

Love Pandas and it has taken me from a 800 line complicated program to a 400 line walk in the park that zooms. Thank you :)

解决方案

You were so close:

In [1]: df.groupby('one').agg(lambda x: "|".join(x.tolist()))

Out[1]:

two

one

1 x|y

2 y|z

3 z

Expanded answer to handle sorting and take only the set:

In [1]: df = DataFrame({'one':[1,1,2,2,3], 'two':list('xyyzz'), 'three':list('eecba')}, index=list('abcde'), columns=['one','two','three'])

In [2]: df

Out[2]:

one two three

a 1 x e

b 1 y e

c 2 y c

d 2 z b

e 3 z a

In [3]: df.groupby('one').agg(lambda x: "|".join(x.order().unique().tolist()))

Out[3]:

two three

one

1 x|y e

2 y|z b|c

3 z a