Function Calling Another Function in Python

To have one function call another, just place the function call within the body of the first function. Here's a simple illustration:

Python

def greet(name):
    print("Hello,", name + "!")

def introduce():
    name = input("Enter your name: ")
    greet(name)  # introduce() calls greet()

introduce()  # Start the program execution

Explanation

1. greet(): Takes a name and prints a greeting.

2. introduce(): Gets the user's name and calls greet() to display the greeting.

3. Program flow: You call introduce(), which in turn calls greet().

Key Benefits

• Modularity: Break your code into smaller, self-contained units, making it easier to manage and debug.

• Reusability: Write functions that can be called from multiple places in your code, avoiding duplication.

• Abstraction: Focus on the high-level logic of what a function needs to do instead of getting buried in implementation details in every part of your program.

Example: Factorial calculation

Python

def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n-1)  # Recursive call

result = factorial(5)
print(result)  # Output: 120

Important Considerations

• Return Values: A function can return a value, and this returned value can be used by the calling function:
  Python
  def add(x, y):
      return x + y
  
  result = add(5, 3)
  print(result)  # Output: 8
  
  

• Recursion: A function can call itself (recursion), elegantly solving problems like calculating factorials or the Fibonacci sequence.

.

Example 1: Area Calculator

Python

def calculate_rectangle_area(length, width):
    return length * width

def calculate_triangle_area(base, height):
    return 0.5 * base * height

def get_shape_area():
    shape = input("Enter shape (rectangle or triangle): ")

    if shape == "rectangle":
        length = float(input("Enter length: "))
        width = float(input("Enter width: "))
        area = calculate_rectangle_area(length, width)
    elif shape == "triangle":
        base = float(input("Enter base: "))
        height = float(input("Enter height: "))
        area = calculate_triangle_area(base, height)
    else:
        print("Invalid shape")
        return

    print("The area is:", area)

get_shape_area()

Example 2: User Authentication

Python

def get_username_password():
    username = input("Enter username: ")
    password = input("Enter password: ")
    return username, password

def check_credentials(username, password):
    # Replace with your actual authentication logic
    if username == "admin" and password == "secret":
        return True
    else:
        return False

def login():
    username, password = get_username_password()
    if check_credentials(username, password):
        print("Login successful!")
    else:
        print("Invalid credentials.")

login()

Example 3: Recursive Fibonacci Sequence

Python

def fibonacci(n):
    if n <= 1:
        return n
    else:
        return fibonacci(n-1) + fibonacci(n-2)

nterms = int(input("Enter number of terms in Fibonacci sequence: "))

if nterms <= 0:
    print("Please enter a positive integer.")
else:
    print("Fibonacci sequence:")
    for i in range(nterms):
        print(fibonacci(i))

Function Calling Another Function in Python¶

In [4]:

def greet(name):
    print("Hello,", name + "!")

def introduce():
    name = input("Enter your name: ")
    greet(name)  # introduce() calls greet()

introduce()

Enter your name: venkat
Hello, venkat!

In [7]:

def Introduce():
    name = input('enter name')
    greet(name)
def greet(customer):
    print("hi ",customer, ' welcome to Vlrtraining' )
    
Introduce()

enter namemohan
hi  mohan  welcome to Vlrtraining

In [6]:

enter namevenkat
hi  venkat  welcome to Vlrtraining

In [11]:

def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n-1)  # Recursive call
value = int(input('enter Number'))
result = factorial(value)
print(result)  # Output: 120 

enter Number6
720

In [13]:

def fact(n):
    if n==0:
        return 1
    else:
        return n * fact(n-1)
value = int(input('enter Number'))
result = fact(value)
print(result)  # Output: 120 

enter Number3
6

In [15]:

def calculate_rectangle_area(length, width):
    return length * width

def calculate_triangle_area(base, height):
    return 0.5 * base * height

def get_shape_area():
    shape = input("Enter shape (rectangle or triangle): ")

    if shape == "rectangle":
        length = float(input("Enter length: "))
        width = float(input("Enter width: "))
        area = calculate_rectangle_area(length, width)
    elif shape == "triangle":
        base = float(input("Enter base: "))
        height = float(input("Enter height: "))
        area = calculate_triangle_area(base, height)
    else:
        print("Invalid shape")
        return 

    print("The area is:", area)

get_shape_area()

Enter shape (rectangle or triangle): ere
Invalid shape

In [16]:

a,b=10,30
a

Out[16]:

10

In [17]:

b

Out[17]:

30

In [18]:

def get_username_password():
    username = input("Enter username: ")
    password = input("Enter password: ")
    return username, password

def check_credentials(username, password):
    # Replace with your actual authentication logic
    if username == "admin" and password == "secret":
        return True
    else:
        return False

def login():
    username, password = get_username_password()
    if check_credentials(username, password):
        print("Login successful!")
    else:
        print("Invali
              d credentials.")

login()

Enter username: venkat
Enter password: vlr
Invalid credentials.

In [19]:

def fibonacci(n):
    if n <= 1:
        return n
    else:
        return fibonacci(n-1) + fibonacci(n-2)

nterms = int(input("Enter number of terms in Fibonacci sequence: "))

if nterms <= 0:
    print("Please enter a positive integer.")
else:
    print("Fibonacci sequence:")
    for i in range(nterms):
        print(fibonacci(i))

Enter number of terms in Fibonacci sequence: 4
Fibonacci sequence:
0
1
1
2

In [ ]: