Python Fundamentals

Notes Part-1  ----- >   PYTHON

Notes Part-2 ------> Input and Output Statements

Notes Part-3  ------> Conditional Statements

Notes Part-4 -------> Operators in python

Notes Part-5  ------>  Datatypes in python

Notes Part -6.1 ------>  Lists

Notes Part- 6.2   -----> Dictionary

Reference Notes on For Loop and While Loop to read:

1. For Loop:

• A for loop is typically used when the number of iterations is known in advance.
• It is structured for cases where you need to iterate over a range, a sequence, or a collection (like a list or a string).

Syntax:

for i in range(start, stop, step):

    # Loop body

Example with a for loop:

n = int(input("enter number"))

s = 0

for i in range(1, n+1):

    s = s + i

    print("sum =", s)

This version iterates over a known range, starting from 1 to n. When n = 5, 

the output will be:

sum = 1

sum = 3

sum = 6

sum = 10

sum = 15

2. While Loop:

• A while loop is generally used when the number of iterations is unknown, and the loop continues based on a condition.
• It keeps running until the condition becomes False.

Syntax:

while condition:

    # Loop body

Example with a while loop:

n = int(input("enter number"))

s = 0

i = 1

while i <= n:

    s = s + i

    print("sum =", s)

    i += 1  # Increment the counter to avoid infinite loop

The output will be the same as the for loop for n = 5.

Key Differences Between for and while Loops: 

• For Loop:

  • Used when the number of iterations is known beforehand (e.g., iterating through a sequence, a fixed range).
  • Easier to read when working with definite ranges or collections.

• While Loop:

  • Used when the number of iterations is unknown, and it depends on some condition.
  • Can be more flexible for dynamic conditions, where the loop may run indefinitely or stop based on a variable condition.

When to Use Each:

• Use a for loop:

  • When you have a clear start and end point.
  • When you are iterating over a collection, sequence, or range.
  • Example: Iterating over numbers 1 to 5, iterating over elements in a list.

• Use a while loop:

  • When you don't know how many iterations you need in advance, but you know the condition that will stop the loop.
  • When you need more control over how and when the loop should stop.
  • Example: Reading a file until the end, looping until the user inputs a specific value.