A function a sequence of statements which perform computation.Functions makes it possible to reuse the code.In Python we have two kinds of functions,built-in functions and user defined function.The creators of Python, wrote a set of functions to address most common problems.And included them as a part of standard Python installation.
Examples:
len(), abs(), int(), str(), print(), input(), open() etc..
Functions which are written by user, other than built-in functions,to solve a problem. A function is a reusable code,which takes arguments as inputs, does some computation, and returns a result. Some function takes arguments, some don’t,Like wise some function return result, and some don’t. Functions that do not return implicitly return the value None.
An argument is a value passed to a function as an input during a function call. In Python its possible to have different options to pass arguments.
Four types of Arguments:
The calculator exercise is still fresh in our mind. Following code reminds us of the basic function.
def add(num1, num2):
return num1 + num2
# Here both num1, num2, argument values are required at function call.
sum = add(10,20)
print(sum)
Exercise 1: Simple calculator
let’s implement a calculator featured with addition, subtraction, multiplication and division.
When funciton is defined with default values for arguments, passing values during function call is optional. Its possible to have default values for arguments.
def add(num1=10, num2=30):
return num1 + num2
#add called with no arguments
sum1 = add()
print("Sum is: ", sum1)
#add called with one arguments
sum2 = add(30)
print("Sum is: ", sum2)
#add called with two arguments
sum3 = add(60, 50)
print("Sum is: ", sum3)
Passing variable number of arguments. Most functions designed to work on fixed set of arguments. But some can handle any number of arguments. In Python its possible to pass varialbe arguments.
Lets see an example of this:
def sum_numbers(*args):
sum = 0
for i in args:
sum += i
return sum
# Multiple arguments
sum_numbers(1,2,3,4,5,6)
# Or just two arguments
sum_numbers(1,2)
# Or no argument
sum_numbers()
Exercise 2: Choose classes you like
Given a funtion with two arguments, one of which is a positional argument, another is an optional argument. Postiional argument is class(es) available to choose, optional argument is a list of class(es) you have chosen. Please choose your favorite class(es) and return in the list.
def favorite_class(*classes, my_favorite=[]):
# Loop through the class(es), choose prefered classes by if...else conditionals
return my_favorite
Variable number of keyword arguments, with key value pair passed to funciton.
def user_details(**kwargs):
for key, value in kwargs.items():
print("Keyword args : ".format(key, value))
# Pass single key value pair
user_details(name='Alim')
# Pass multiple key value pairs
user_details(name='Alim', age=28, country='China')
Often a function takes arguments, does some computation, and returns a result. The return keyword is used for this. To get the result it has to be assigned to a variable, at the function call.
For example:
def return_min_and_max(numbers):
return min(numbers), max(numbers)
min_and_max_value = return_min_and_max([32,1,43,564,23,675,234])
print('Min value is: ', min_and_max_value[0]
print('Max value is: ', min_and_max_value[1]
Exercise 3: Write an algorithm to return Min and Max in a single function
def min_max(numbers):
min_value = 0
max_value = 0
# Write an algorithm to return two values together
return min_value, max_value
Global scope
Global variables can be accessed from anywhere
Local scope
Local variables can be accessed only in block where defined
Nonlocal scope
Accessible only in enclosing blocks(Inner functions, clousers)
Example 1:
x = 2
def var_scope():
y = 30
print("I'm x and I'm global ", x)
print("I'm y and I'm local ", y)
var_scope()
# output:
"I'm x and I'm global 2"
"I'm y and I'm local 30"
Example 2:
x = 2
def var_scope():
y = 30
x = 20
print("I'm x and I'm local ", x)
print("I'm y and I'm local ", y)
print("I'm x and I'm global ", x)
var_scope()
# Output:
"I'm x and I'm global 2"
"I'm x and I'm local 20"
"I'm y and I'm local 30"
Homework: Students’ score management system
Finals are coming, students are working hard on their exam preparation. Moreover, there is a big concern, it’s becoming a challenge to manage student’s scores. Headmaster made an announcement to let students who have coding skills to develop a ‘Students exam score management system’ to simplify the score management process. Could you please design a program which has arbitrary number of following features?
Required feature:
def add_students_info(*names, *scores):
# Do looping and adding
Optional features:
Categorize students by three leves and return in search result.
For example:
Possible outputs:
def students_info(student_name):
# Do the searching
return name, class, category
# Outputs
Frank Math A