python Function

PRESENTED BY,
RONAK RATHI & SAMIR
RAWAT.

OBJECTIVE
HOW TO DEFINE A FUNCTION
HOW TO CALL A FUNCTION
FUNCTION ARGUMENTS
FUNCTION RECURSION

FUNCTION
 FUNCTION IS A GROUP OF RELATED
STATEMENTS THAT PERFORM A SPECIFIC TASK
 FUNCTIONS HELP BREAK OUR PROGRAM INTO
SMALLER AND MODULAR CHUCKS

DEFINING FUNCTION
def marks the start of function
function name to uniquely
identify a function.
def function_name (parameter) :
Argument to pass a value in function
colon(:) to mark end of
function header

EXAMPLE OF FUNCTION
def greet (name):
print(“Hello,” + name +” . Good afternoon!”)

CALLING A FUNCTION
HOW TO CALL A FUNCTION?
Once we have defined a function, we can call it from
another function, program or even the Python prompt.
To call a function we simply type the function name
with appropriate parameters.
>>> greet(“everyone")
>>>Hello, everyone. Good afternoon!

EXAMPLE
def my_func():
x = 10
global y
y = 20
print("Value of y inside function:",x)
print("Value of y inside function:",y)
x = 20
y = 10
my_func()
print("Value of y outside function:",x)
print("Value of y outside function:",y)

THERE ARE TWO TYPES OF FUNCTION IN PYTHON
 BUILT-IN FUNCTION
Example: print(), input(), eval().
 USERDEFINE FUNCTION
Example: def my_addition(x,y):
sum = x + y
return sum

 FUNCTION BUILT WITHIN THE PYTHON.
 THERE ARE 68 BUILT-IN FUNCTION VERSION 3.4.
 CHANGES WITH RESPECT TO UPDATED VERSION.

VARIABLE
FUNCTION
ARGUMENTS
DEFAULT
ARGUMENT
KEYWORD
ARGUMENT
ARBITRARY
ARGUMENTS

DEFAULT ARGUMENTS
 Default value to function argument is passed using
assignment operator ‘ = ‘.
Example:
def greet(name, msg = "Good morning!"):
print("Hello, " name + ', ' + msg)
 Non-default argument cannot follow default argument
Example: def greet(msg = "Good morning!", name):
SyntaxError:
non-default argument follows default argument

KEYWORD ARGUMENTS
 When we call a function with some values, these
values get assigned to the arguments according to their
position .
 Keyword arguments follows positional argument.

EXAMPLE OF KEYWORD
ARGUMENT
 greet(name = "Bruce",msg = "How do you do?")
2 keyword arguments
 greet(msg = "How do you do?",name = "Bruce")
2 keyword arguments (out of order)
 greet("Bruce",msg = "How do you do?")
1 positional, 1 keyword argument
 greet(name="Bruce","How do you do?")
SyntaxError:
non-keyword arg after keyword arg

 If number of arguments unknown we use arbitrary
arguments
 ( * ) Asterisk before arguments define arbitrary arguments.
Example:
def greet(*names):
for name in names:
print("Hello",name)
>>>greet("Monica","Luke","Steve","John")
ARBITRARY ARGUMENTS

 Like other programming language in python, function
can call itself.
 Definition of recursion in python is same as other
programming lang. -> C, C++, C#, Java etc.

def recur_fact(x):
if x == 1:
return 1
else:
return (x * recur_fact(x-1))
num = int(input("Enter a number: "))
if num >= 1:
print("The factorial of", num, "is", recur_fact(num))
EXAMPLE OF RECURSION

 Function without function name.
 Function is defined using lambda keyword, hence
function is also called Lambda function.
 Used for short period in python.
 Can have any number of arguments but only single
expression.
 Specially used with built-in functions like filter(),
map() etc.
ANONYMOUS

 double = lambda x: x * 2 print(double(5))
 my_list = [1, 5, 4, 6, 8, 11, 3, 12]
new_list = list(filter(lambda x: (x%2 == 0) , my_list))
print(new_list)
EXAMPLE OF LAMBDA
FUNCTION

RESOURCES
 www.programiz.com/python-programming
 https://wiki.python.org/moin/BeginnersGuide/Progra
mmers

python Function

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