ESIT135: Unit 3 Topic: functions in python

Prepared by,
Prof. S. S. Gawali
Computer Engineering
Sanjivani College of Engineering, Kopargaon-423 603
Department of Computer Engineering
Sanjivani Rural Education Society’s

 Function is a reusable block of statements used to perform a specific task.
 Function is execute only when we called.
Department of Computer Engineering, Sanjivani College of Engineering, Kopargaon 2

 The idea of function is to put some commonly or repeatedly done tasks together and
make a function so that instead of writing the same code again and again for different
inputs, we can do the function calls to reuse code contained in it over and over again.

 There are two types of function in Python programming:
 Standard library functions - These are built-in functions in Python that are
available to use.
 Example: type(), input(), print(), int(), float()
 User-defined functions - We can create our own functions based on our
requirements.
4
Department of Computer Engineering, Sanjivani College of Engineering, Kopargaon

 In Python a function is defined using the def keyword:
 Syntax:
5

 def - keyword used to declare a function
 function_name - any name given to the function
 parameters - are place holders that define the parameters that go into the function.
 return (optional) - returns value from a function

 The terms parameter and argument can be used for the same thing: information that
are passed into a function.
 From a function's perspective:
 A parameter is the variable listed inside the parentheses in the function definition.
 An argument is the value that is sent to the function when it is called.
7

def hello():
''' Function to print Hello.'‘’
print("Hello")

 After creating a function we can call it by using the name of the function followed by
parenthesis containing parameters of that particular function.

def hello():
''' Function to print hello.'‘’
print("Hello")
hello()
Output
Hello

 1. Positional arguments.
 2. Keyword arguments.
 3. Default arguments.
 4. Variable length arguments.

 A positional parameter/argument in Python is a parameter/ an argument whose position
matters in a function call.
 Syntax: call_func(arg1, arg2, arg3)
 Example: Define a function that shows info about a person given the name and age:
def p_info(name, age):
'''Person infrormation.'‘’
print(f"Hi, I am {name}. I am {age} years old.")
#Call this function with two positional arguments name and age.
p_info("Rina",31)
Output:
Hi, I am Rina. I am 31 years
old.

 A keyword argument in Python means that a function argument has a name label.
 Syntax: call_func(arg_name=arg1)
 def p_info(name, age):
 '''Person infrormation.'''
 print(f"Hi, I am {name}. I am {age} years old.")
 p_info(name="Siya",age=40)
 p_info(age=31,name="Rina")
Output:
Hi, I am Siya. I am 40 years
old
Hi, I am Rina. I am 31 years
old

 Default arguments in Python represent the function arguments that will be used if no
arguments are passed to the function call.
 The default arguments are represented as parameter_name = value in the function
definition.
 Syntax: call_func(par_name=arg1)
def p_info(name="Priya", age=20): # function creation with default parameter/ argument
'''Person infrormation.'''
print(f"Hi, I am {name}. I am {age} years old")
p_info(name="Siya",age=40)
p_info()
Output:
Hi, I am Siya. I am 40 years
old
Hi, I am Priya. I am 20 years
old

 Return statement use to return values.
 Function can take input values as parameters and execute statements, and
returns output to caller with return statement.
 Two way to return value from function:
 Return a value
 Return multiple values

 To let a function return a value, use the return statement:
 Example:
def sq(x):
return x * x
print(sq(3))
print(sq(5))
print(sq(9))
Output:
9
25
81

 In python, a function can return any number of values.
 Example:
def sq_cu(x):
return x * x, x*x*x
print(sq_cu(10)
a,b=sq_cu(5)
print(a)
print(b)
Output:
(100,1000)
25
125

 Variable: Variables are the containers for storing data values.
 Scope of Variable: The location where we can find a variable and also access it if
required is called the scope of a variable.
 Based on the scope, we can classify Python variables into three types:
 1. Local Variables
 2. Global Variables

 The variables which are declared outside of function are called global variables.
 These variables can be accessed in all functions of that module.
 Example: Create global variable to Print Square and cube of number using function.
a=5 # a is global variable
def sq():
print(a*a)
def cu():
print(a*a*a)
sq()
cu()
Output
25
125

 The variables which are declared inside a function are called local variables.
 Local variables are available only for the function in which we declared it. i.e from
outside of the
 function we cannot access.
 Example: Create a function to display the square of numbers using local variable.
def sq():
a=5 # a is local variable
print(a*a)
sq()
Output
25

 Sometimes we can declare a function without any name, such types of nameless
functions are called anonymous functions or lambda functions.
 The main purpose of the anonymous function is just for instant use (i.e for one-time
usage)

 We can define by using lambda keyword
 Syntax:
 lambda arg_list:expression
 Example
 lambda n:n*n # to calculate n square

 A Python module is a file containing Python definitions and statements.
 A module can define functions, classes, and variables.
 A module can also include runnable code.
 Grouping related code into a module makes the code easier to understand and use.
 It also makes the code logically organized.

 Built-in Modules.
 User-defined Modules.

 One of the feature of Python is “rich standard library”.
 This rich standard library contains lots of built-in modules.
 Hence, it provides a lot of reusable code.
 To name a few, Python contains modules like “math”, “sys”, “datetime”, “random”.

 User can create module as per requirement is called user defined module.

 The import keyword to import both built-in and user-defined modules in Python.
 Different way to import module
 Syntax 1: import module_name
 Syntax 2: import module_name as rename_of_module
 Syntax 3: from module_name import method/constant-variable
 Syntax 4: from module_name import method1/constant-var1, method2/constant-
var2…..
 Syntax 5: from module_name import *
 Syntax6: from module_name import method/constant as rename_of_method/constant

import module_name
 Example:
import math
a=5
print(math.sqrt(a))
print(math.factorial(a))
print(math.pi)
Output:
2.23606797749979
120
3.141592653589793

import module_name as rename_of_module
 Example:
import math as m
a=int(input(“Enter no.”))
print(sqrt(a)) Output:
Enter no. 16
4.0

from module_name import method/constant-variable
 Example:
from math import sqrt
print(sqrt(a))
Output:
Enter no. 16
4.0

from module_name import method1/constant-variable1, method2/constant-
variable2…..
 Example:
from math import sqrt, pi, pow
print(sqrt(a))
print(pi)
print(pow(a,3))
Output:
Enter no.2
1.4142135623730951
3.141592653589793
8.0

from module_name import *
 Example:
from math import *
print(sqrt(a))
print(pi)
print(pow(a,3))
Output:
Enter no.3
1.7320508075688772
3.141592653589793
27.0

from module_name import method/constant as rename_of_method/constant
 Example:
from math import factorial as f
print(f(a)) Output:
Enter no.5
120

ESIT135: Unit 3 Topic: functions in python

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