Python functions PYTHON FUNCTIONS1234567

FUNCTION
S
 If a group of statements is repeatedly required then it is not
recommended to write these statements everytime
seperately.
 We have to define these statements as a single unit and we
can call that unit any number of times based on our
requirement without rewriting.
 This unit is nothing but function.
 The main advantage of functions is code Reusability

Python supports 2 types of functions
1. Built in Functions
2. User Defined Functions
2. Built in Functions:
The functions which are coming along with Python
software automatically,are called built in functions or
pre defined functions
Eg:
id()
type()
input()
eval() etc..

User Defined
Functions
The functions which are developed by programmer
explicitly according to business requirements ,are called
user defined functions.
Syntax to create user defined functions:
def function_name(parameters) :
""" doc string"""
----
-----
return value

Note: While creating functions we can use 2
keywords 1. def (mandatory)
2. return (optional)
Eg 1: Write a function to print
Hello 1) def wish():
2) print("Hello Good
Morning")
3) wish()
4) wish()
5) wish()

Parameter
s
 Parameters are inputs to the function.
 If a function contains parameters, then at the time of
calling, compulsory we should provide values otherwise we
will get error.
Eg: Write a function to take name of the student as input and
print wish message by name.
1. def wish(name):
2. print("Hello",name," Good Morning")
3. wish("Durga")
4. wish("Ravi")
7. D:Python_classes>py test.py
8. Hello Durga Good Morning
9. Hello Ravi Good Morning

Eg: Write a function to take number as input and print its
square value 1. def squareIt(number):
2. print("The Square of",number,"is", number*number)
3. squareIt(4)
4. squareIt(5)
7. The Square of 4 is 16
8. The Square of 5 is 25
Parameter
s

Return
Statement
Function can take input values as parameters and executes
business logic, and returns output to the caller with return
statement.
Q. Write a function to accept 2 numbers as input and return
sum.
1. def add(x,y):
2. return x+y
3. result=add(10,20)
4. print("The sum is",result)
5. print("The sum is",add(100,200))
9. The sum is 30

Eg:
1. def f1():
2.
print("Hello")
3. f1()
4. print(f1())
Output
7. Hello
8. Hello
9. None
EVEN/ODD program
1. def even_odd(num):
2. if num%2==0:
3. print(num,"is Even
Number")
4. else:
5. print(num,"is Odd
Number")
6. even_odd(10)
7. even_odd(15)
Output
11. 10 is Even Number
12. 15 is Odd Number

Factorial of a Number
1) def fact(num):
2) result=1
3) while num>=1:
4) result=result*num
5) num=num-1
6) return result
7) for i in range(1,5):
8) print("The Factorial
of",i,"is :",fact(i))
Output
12) The Factorial of 1 is : 1

Returning multiple values from a
function
In other languages like C,C++ and Java, function can return
atmost one value. But in Python, a function can return any
number of values.
1)def sum_sub(a,b):
2) sum=a+b
3) sub=a-b
4) return sum,sub
5) x,y=sum_sub(100,50)
6) print("The Sum is :",x)
7) print("The Subtraction
is :",y)
Output
10) The Sum is : 150
11) The Subtraction is : 50
1) def calc(a,b):
2) sum=a+b
3) sub=a-b
4) mul=a*b
5) div=a/b
6) return
sum,sub,mul,div
7) t=calc(100,50)
8) print("The Results
are")

Types of
arguments
def f1(a,b):
------
------
------
f1(10,20)
a,b are formal
arguments where
as 10,20 are actual
argument
There are 4 types are actual
arguments are allowed in
Python.
1. positional arguments
2. keyword arguments
3. default arguments
4. Variable length arguments

These are the arguments passed to function in correct positional
order.
def sub(a,b):
print(a-b)
sub(100,200)
sub(200,100)
 The number of arguments and position of arguments must be
matched.
 If we change the order then result may be changed.
 If we change the number of arguments then we will get error.
positional
arguments:

keyword
arguments
We can pass argument values by keyword i.e by parameter
name.
1. def wish(name,msg):
2. print("Hello",name,msg)
3. wish(name="Durga",msg="Good Morning")
4. wish(msg="Good Morning",name="Durga")
5.
6. Output
Here the order of arguments is not important but number of

Note: We can use both positional and keyword arguments
simultaneously. But first we have to take positional
arguments and then keyword arguments,otherwise we will
get syntaxerror.
keyword
arguments
def wish(name,msg):
print("Hello",name,msg)
wish("Durga","GoodMorning") ==>valid
wish("Durga",msg="GoodMorning") ==>valid
wish(name="Durga","GoodMorning") ==>invalid
SyntaxError: positional argument follows keyword

Default
Arguments
Sometimes we can provide default values for our positional
arguments.
1) def wish(name="Guest"):
2) print("Hello",name,"Good Morning")
3)
4) wish("Durga")
5) wish()
6)
7) Output
8) Hello Durga Good Morning
9) 9) Hello Guest Good Mornin
 If we are not passing any name then only default value will be

*Note: After default arguments we should not take non
default arguments
def wish(name="Guest",msg="Good Morning"):
===>Valid
def wish(name,msg="Good Morning"): ===>Valid
def wish(name="Guest",msg): ==>Invalid
SyntaxError: non-default argument follows default
argument
Default
Arguments

Variable length
arguments
 Sometimes we can pass variable number of arguments to
our function,such type of arguments are called variable
length arguments.
 We can declare a variable length argument with * symbol
as follows
 def f1(*n):
 We can call this function by passing any number of
arguments including zero number.
 Internally all these values represented in the form of tuple.

Variable length
arguments
1) def sum(*n):
2) total=0
3) for n1 in n:
4) total=total+n1
5) print("The
Sum=",total)
7) sum()
8) sum(10)
9) sum(10,20)
10) sum(10,20,30,40) 11)
12) Output
13) The Sum= 0
14) The Sum= 10
15) The Sum= 30
1) def f1(n1,*s):
2) print(n1)
3) for s1 in s:
4) print(s1)
5)
6) f1(10)
7) f1(10,20,30,40)
8)
f1(10,"A",30,"B")
Output
11) 10
12) 10
13) 20
14) 30
15) 40
16) 10
17) A
18) 30
19) B

Types of
Variables
Python supports 2 types of
variables.
1. Global Variables
2. Local Variables
1. 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.
2. Local Variables:
 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 function
we cannot access.

1) a=10 # global
variable
2) def f1():
3) print(a)
4)
5) def f2():
6) print(a)
7)
8) f1()
9) f2()
10)
11) Output
12) 10
1) def f1():
2) a=10
3) print(a) # valid
4)
5) def f2():
6) print(a) #invalid
7)
8) f1()
9) f2()
10)
11) NameError: name
'a' is not defined
Types of
Variables

global
keyword
We can use global keyword for the following 2 purposes:
1. To declare global variable inside function
2. To make global variable available to the function so that
we can perform required modifications
1) a=10
2) def f1():
3) a=777
4) print(a)
6) def f2():
7) print(a)
9) f1()
10) f2()
12) Output
13) 777
14) 10
1) a=10
2) def f1():
3) global a
4) a=777
5) print(a)
7) def f2():
8) print(a)
10) f1()
11) f2()
13) Output
14) 777
15) 777

Python functions PYTHON FUNCTIONS1234567

Python functions PYTHON FUNCTIONS1234567

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Python functions PYTHON FUNCTIONS1234567