Python Function Basics

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Run Your Python Programs Online

Computer Science 

( Class XII Sc ) 

( Subject Code 083)



Learn the concept of function in python and attempt the quiz 

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Function

• Function is a block of code that perform a particular task
• It only runs when it is invoked or called. 
• You can pass data, known as parameters, into a function.
•  A function can return data as a result using return keyword.

Types of functions

1. User Defined : defined by the user using def keyword
2. built-in functions: Predefined function in python language

Creating/Defining Function:

def my_function():
  print("Hello from a function")

Calling Function

my_function()

Parameters(arguments): information passed in a function during creation or calling is called parameters.

def sum(a,b):

        s=a+b

        print(s)

x=10

y=20

sum(x,y)

# a , b  and x,y are called parameters.

Actual parameters: parameters passed in function calling. In above code x and y are actual parameters

Formal parameters: parameters passed in function definition. In above code a and b are formal parameters

Function return value using return keyword

def sum(a,b):

        s=a+b

        return s

x=10

y=20

n=(x,y)

print(n)

A function can return multiple values

# This function returns a tuple

def fun():

    str = "ajay"

    x   = 20

    return str, x;  # Return tuple, we could also write (str, x)

str, x = fun() # Assign returned tuple

print(str)

print(x)

A function can return multiple values using list or tuple or dictionary

# This function returns a tuple

def fun():

    str = "mukesh"

    x   = 20

    return str, x;  # Return tuple, we could also write (str, x)

t = fun() # Assign returned tuple

print(t)

output:

('mukesh', 20)

# This function returns a dictionary

def fun():

    d = dict(); 

    d['str'] = "abc"

    d['x']   = 20

    return d

  

# Driver code to test above method

d = fun() 

print(d) 

# This function returns a list

def fun():

    str = “abc"

    x = 20   

    return [str, x];  

  

# Driver code to test above method

list = fun() 

print(list)

Variable length argument: 

We can pass any number of arguments in a functon using * symbol.

# sum of n mumbers using variable length arguments with function
def sum(*n):
              m=n[0]
              for i in n:
                            s=s+i
              print(s)

sum(2,5,6)
sum(12,15,6)
sum(22,5,6,2.5)

#Find largest number among given numbers
def maximum(*n):
    m=0
    for i in n:
        if(i>m):
            m=i
    return m

print(maximum(1,2,3,4)) # 4
print(maximum(11,22,3,934,66,77,88,555))   #555
print(maximum(111,2,3,4,66,7,8,555,33)) #555

Function with Default Arguments

Default Arguments: Function arguments can have default values in Python. We can provide a default value to an argument by using the assignment operator (=). Here is an example.

If we don’t pass any value to the function then it will take a pre defined value. 

def hello(name, msg = "Good morning!"):

  print("Hello",name + ', ' +msg)

hello("mukesh")

hello("Modi","How do you do?")

Note 

->Any number of arguments in a function can have a default value. 

->non-default arguments cannot follow default arguments. 

For example, if we had defined the function header above 

def hello(msg = "Good morning!", name):

SyntaxError: non-default argument follows default argument

Positional Arguments 
We cannot change the position of arguments.
if change the output will be changed.

def sub(a,b):
              print(a-b)

sum(20,35) # 20 will be assigned in a and 35 will be assigned in b
sum(35,20) # 35 will be assigned in a and  20 will be assigned in b


 Keyword Arguments 

When we Call above function with their arguments name . Then we need not to remember the  position of arguments

ef sub(a,b):
              print(a-b)

sum(a=20,b=35) # 20 will be assigned in a and 35 will be assigned in b
sum(n=35, a=20) # 35 will be assigned in a and  20 will be assigned in b

output

-15
-15





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