Function Call Stack & Recursion

 Stack

Stack is a data structure that stores items in an Last-In/First-Out manner.

Calling a Function

Calling

function_1()

inside

function_2()

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def get_largest_sqr(list_x):

len_list = len(list_x)

for i in range(len_list):

x = list_x[i]

list_x[i] = x * x

largest = max(list_x)

return largest

list_a = [1,-3,2]

result = get_largest_sqr(list_a)

print(result)

PYTHON

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Output

9

In the above code calling functions are

len()

and

max()

inside

get_largest_sqr()

Sum of Squares of List Items

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def get_sqrd_val(x):

return (x * x)

def get_sum_of_sqrs(list_a):

sqrs_sum = 0

for i in list_a:

sqrs_sum += get_sqrd_val(i)

return sqrs_sum

list_a = [1, 2, 3]

sum_of_sqrs = get_sum_of_sqrs(list_a)

print(sum_of_sqrs)

PYTHON

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Output

14

Function Call Stack

Function Call Stack keeps track of function calls in progress

Recursion

A function calling itself is called a Recursion

Let's understand recursion with a simple example of multiplying N numbers

Multiply N Numbers

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def factorial(n): # Recursive Function

if n == 1: # Base Case

return 1

return n * factorial(n - 1) # Recursion

num = int(input())

result = factorial(num)

print(result)

PYTHON

Base Case

A recursive function terminates when base condition is met

Input

3

Output

6

Without Base case

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def factorial(n):

return n * factorial(n - 1)

num = int(input())

result = factorial(num)

print(result)

PYTHON

Input

3

Output

RecursionError: maximum recursion depth exceeded