如何获得数据框中每个单独分组的项目的均值 uisng pandas？

Question

import numpy as np 
import pandas as pd
df=pd.DataFrame({'birds': ['Cranes', 'Cranes', 'plovers', 'spoonbills', 'spoonbills', 'Cranes', 'plovers', 'Cranes', 'spoonbills', 'spoonbills'],
                 'age': [3.5, 4, 1.5, np.nan, 6, 3, 5.5, np.nan, 8, 4],
                 'visits': [2, 4, 3, 4, 3, 4, 2, 2, 3, 2],
                 'priority': ['yes', 'yes', 'no', 'yes', 'no', 'no', 'no', 'yes', 'no', 'no']},index= ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j'])

df 

From this I need to calculate the mean age for each different birds in dataframe.

Here is my code

df1=df.get_group('Cranes')
print(df1)
df1[['age']].mean()

df3=df.get_group('plovers')
print(df3)
df3.mean()

df4=df.get_group('spoonbills')
print(df4)
df4.mean()

Output I am getting is 

   birds  age  visits priority
a  Cranes  3.5       2      yes
b  Cranes  4.0       4      yes
f  Cranes  3.0       4       no
h  Cranes  NaN       2      yes
     birds  age  visits priority
c  plovers  1.5       3       no
g  plovers  5.5       2       no
        birds  age  visits priority
d  spoonbills  NaN       4      yes
e  spoonbills  6.0       3       no
i  spoonbills  8.0       3       no
j  spoonbills  4.0       2       no

Out[33]:

age       6.0
visits    3.0
dtype: float64

which is mean of age from all groups.But I need the mean to get displayed under each group such as mean for cranes , mean for plovers and mean for spoonbills seperatley . What modification is needed to the code ? Kinldy help

Answer 1

As the comments suggest you can use groupby and then mean

To get a Pandas Series:

df.groupby('birds').mean()['age']

Results in:

birds
Cranes        3.5
plovers       3.5
spoonbills    6.0
Name: age, dtype: float64

To get a DataFrame, you can reset the index:

df.groupby('birds').mean()['age'].reset_index()

Resulting in:

        birds  age
0      Cranes  3.5
1     plovers  3.5
2  spoonbills  6.0