How to define user defined function in pandas

Question

I have a csv file that contains information like

name    salary  department
a        2500      x
b        5000      y
c        10000      y
d        20000      x 

I need to convert this using Pandas to the form like

dept    name    position
x        a       Normal Employee
x        b       Normal Employee
y        c       Experienced Employee
y        d       Experienced Employee

if the salary <=8000 Position is Normal Employee

if the salary >8000 && <=25000 Position is Experienced Employee

My default code for group by

import csv
import pandas
pandas.set_option('display.max_rows', 999)
data_df = pandas.read_csv('employeedetails.csv')
#print(data_df.columns)
t = data_df.groupby(['dept'])
print t

What are the changes i need to make in this code to get the output that i mentioned above

Answer 1

I would use a simple function like:

def f(x):
    if x <= 8000:
        x = 'Normal Employee'
    elif 8000 < x <= 25000:
        x = 'Experienced Employee'
    return x

and then apply it to the df:

df['position'] = df['salary'].apply(f)

Answer 2

You could define 2 masks and pass these to np.where:

In [91]:
normal = df['salary'] <= 8000
experienced = (df['salary'] > 8000) & (df['salary'] <= 25000)
df['position'] = np.where(normal, 'normal emplyee', np.where(experienced, 'experienced employee', 'unknown'))
df

Out[91]:
  name  salary department              position
0    a    2500          x        normal emplyee
1    b    5000          y        normal emplyee
2    c   10000          y  experienced employee
3    d   20000          x  experienced employee

Or slightly more readable is to pass them to loc:

In [92]:
df.loc[normal, 'position'] = 'normal employee'
df.loc[experienced,'position'] = 'experienced employee'
df

Out[92]:
  name  salary department              position
0    a    2500          x       normal employee
1    b    5000          y       normal employee
2    c   10000          y  experienced employee
3    d   20000          x  experienced employee