Functions can be defined to execute specific tasks and can be called when ever needed.
The variables used in a function can be passed as arguments. When you want a specific task to be done multiple times at different points of time, functions come in handy.

← GO BACK : Python basics: Conditionals & Loops

FUNCTIONS

In the below example, we will create an array called ‘classroom’ that contains a few student names.
We will create a function called ‘enroll’ that help us enroll new students to the ‘classroom’.
The function takes the name of the student as an argument, to enroll.

#!/usr/bin/python

#Create an array called classroom
classroom=["student1", "student2", "student3", "student4"] 

#Print student list
print "Current students list:"
print classroom

#Define function enroll
def enroll(new_student ):
   print "Enrolling Student",new_student
   classroom.append(new_student)
   print classroom
   return;
   
#Request student name. Exit when 'exit' is input   
student_name = raw_input("Enter name to enroll : ")
while ( student_name != "exit" ):
   enroll(student_name)
   student_name = raw_input("Enter name to enroll : ")
   continue

As you see in the above example, functions are defined a keyword ‘def’ followed by ‘function-name’ and arguments in braces. The end of the function is marked with ‘return;’. A function block again needs to be intended, to mark the start and end of a block with ‘return;’ in the end. When the function is called, it must be called with the arguments that it was defined to accept. example function_name(arguement).

Below is the output of the example:

Current students list:
['student1', 'student2', 'student3', 'student4']
Enter name to enroll : student5
Enrolling Student student5
['student1', 'student2', 'student3', 'student4', 'student5']
Enter name to enroll : student6
Enrolling Student student6
['student1', 'student2', 'student3', 'student4', 'student5', 'student6']
Enter name to enroll : student7
Enrolling Student student7
['student1', 'student2', 'student3', 'student4', 'student5', 'student6', 'student7']
Enter name to enroll : student8
Enrolling Student student8
['student1', 'student2', 'student3', 'student4', 'student5', 'student6', 'student7', 'student8']
Enter name to enroll : exit

Functions with Multiple arguements and Python dictionary
Functions can take multiple arguments.
Lets Create a function that will not only enroll the student but also records the age.

Instead of using an array to store values, we will create a dictionary in Python. Python dictionary is a set of keys value pairs.

ages={'student1' : '17', 'student2' : '14', 'student3' : '18', 'student4' : '21'}

Lets print all the key value pairs in the dictionary with a for loop.

 for i in ages:
   print i,ages[i]

student3 18
student2 14
student1 17
student4 21

Keys can be called by name, example

print ages['student1']

17

Going back to creating a function, we will create one that records name and age as key value pairs in a python dictionary.

#!/usr/bin/python
ages={'student1' : '17', 'student2' : '14', 'student3' : '18', 'student4' : '21'}

print "Current students and their ages are as follows:"
for i in ages:
   print i,ages[i]
def enroll( new_student, age ):
   print "Enrolling Student",new_student,"age :",age
   ages.update({new_student:age})
   for i in ages:
     print i,ages[i]
   return;
student_name = raw_input("Please enter student name : ")
age = raw_input("Please enter student age : ")
while ( student_name != "exit" ):
   enroll(student_name,age)
   student_name = raw_input("Please enter student name : ")
   age = raw_input("Please enter student age : ")
   continue

As you see, the example is same as the previous one, however it also takes a second argument and makes use of it in the statements that are in the block.

Thus, when calling the function it should be called with both the arguments, function_name(argument1, argument2).

Current students and their ages are as follows:
student3 18
student2 14
student1 17
student4 21
Please enter student name : student5
Please enter student age : 32
Enrolling Student student5 age : 32
student3 18
student2 14
student1 17
student5 32
student4 21
Please enter student name : student6
Please enter student age : 12
Enrolling Student student6 age : 12
student3 18
student2 14
student1 17
student6 12
student5 32
student4 21
Please enter student name : student7
Please enter student age : 21
Enrolling Student student7 age : 21
student3 18
student2 14
student1 17
student7 21
student6 12
student5 32
student4 21
Please enter student name : student8
Please enter student age : 23
Enrolling Student student8 age : 23
student8 23
student3 18
student2 14
student1 17
student7 21
student6 12
student5 32
student4 21
Please enter student name : exit
Please enter student age :

This site uses Akismet to reduce spam. Learn how your comment data is processed.