将函数应用于pandas中数据框的每一列

I have this:

我有这个：

df = DataFrame(dict(person= ['andy', 'rubin', 'ciara', 'jack'], 
     item = ['a', 'b', 'a', 'c'], 
     group= ['c1', 'c2', 'c3', 'c1'], 
     age= [23, 24, 19, 49]))
df:

    age group item person
0   23  c1    a    andy
1   24  c2    b    rubin
2   19  c3    a    ciara
3   49  c1    c    jack
df = DataFrame(dict(per