if age >= 18:
print("Eligible")
โ Incorrect Indentation
if age >= 18:
print("Eligible")
Python requires proper indentation.
Correct:
if age >= 18:
print("Eligible")
๐น 11. Real-World Data Science Example
prediction = 0.82
if prediction >= 0.5:
print("Spam Email")
else:
print("Not Spam")
Many Machine Learning classification models use similar logic to convert prediction probabilities into categories.
๐ฏ Practice Questions
1. Check whether a number is positive or negative.
2. Check whether a person is eligible to vote.
3. Create a grading system using "if...elif...else".
4. Check whether a number is even or odd.
5. Determine the largest of three numbers.
๐ฏ Key Takeaways
โ Use "if" to execute code when a condition is True.
โ Use "else" to execute code when the condition is False.
โ Use "elif" to check multiple conditions.
โ Nested "if" statements allow more complex decision-making.
โ Logical operators (and, or, not) help combine conditions.
โ The ternary operator provides a concise way to write simple "if...else" statements.
Conditional statements are the foundation of decision-making in Python and are widely used in automation, data analysis, machine learning, and AI applications.
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๐ Data Science Roadmap 2026
๐ Phase 1: Programming Fundamentals
๐ Topic 5: Python Loops ("for" & "while")
Welcome back! ๐
In the previous lesson, you learned how Python makes decisions using if, elif, and else. Now it's time to learn how to repeat tasks automatically using loops.
Loops are one of the most powerful concepts in Python. Instead of writing the same code multiple times, you can use loops to execute a block of code repeatedly.
In Data Science, loops are commonly used to process datasets, automate repetitive tasks, iterate through lists, and build machine learning workflows.
๐น 1. What is a Loop?
A loop is used to execute a block of code multiple times until a condition is met.
Without loops:
Using a loop:
Both produce the same output, but the loop is much shorter and easier to maintain.
๐น 2. Types of Loops in Python
Python provides two main types of loops:
โ "for" Loop
โ "while" Loop
๐น 3. The "for" Loop โญ
A "for" loop is used when you know how many times you want to repeat a task.
Syntax
Example
Output:
Notice that
๐น 4. The "range()" Function โญ
The
Example 1
Output:
Example 2
Output:
Example 3
Output:
The third argument is called the step size.
๐น 5. Looping Through a List
Output:
๐น 6. The "while" Loop โญ
A "while" loop continues executing as long as the condition remains True.
Syntax
Example
Output:
๐น 7. Infinite Loop
Be careful when using "while" loops.
This loop never stops unless interrupted.
Always ensure the condition eventually becomes False.
๐น 8. Loop Control Statements โญ
"break" - Stops the loop immediately
Output:
"continue" - Skips the current iteration
Output:
"pass" - Acts as a placeholder
Useful when writing incomplete code.
๐น 9. Nested Loops
A loop inside another loop.
Output:
๐น 10. Real-World Data Science Example
Calculate the total sales.
๐ Phase 1: Programming Fundamentals
๐ Topic 5: Python Loops ("for" & "while")
Welcome back! ๐
In the previous lesson, you learned how Python makes decisions using if, elif, and else. Now it's time to learn how to repeat tasks automatically using loops.
Loops are one of the most powerful concepts in Python. Instead of writing the same code multiple times, you can use loops to execute a block of code repeatedly.
In Data Science, loops are commonly used to process datasets, automate repetitive tasks, iterate through lists, and build machine learning workflows.
๐น 1. What is a Loop?
A loop is used to execute a block of code multiple times until a condition is met.
Without loops:
print("Hello")
print("Hello")
print("Hello")
print("Hello")
print("Hello")Using a loop:
for i in range(5):
print("Hello")
Both produce the same output, but the loop is much shorter and easier to maintain.
๐น 2. Types of Loops in Python
Python provides two main types of loops:
โ "for" Loop
โ "while" Loop
๐น 3. The "for" Loop โญ
A "for" loop is used when you know how many times you want to repeat a task.
Syntax
for variable in sequence:
# Code to execute
Example
for i in range(5):
print(i)
Output:
0
1
2
3
4
Notice that
range(5) generates numbers from 0 to 4.๐น 4. The "range()" Function โญ
The
range() function generates a sequence of numbers.Example 1
for i in range(5):
print(i)
Output:
0 1 2 3 4Example 2
for i in range(1, 6):
print(i)
Output:
1 2 3 4 5Example 3
for i in range(2, 11, 2):
print(i)
Output:
2 4 6 8 10 The third argument is called the step size.
๐น 5. Looping Through a List
fruits = ["Apple", "Banana", "Mango"]
for fruit in fruits:
print(fruit)
Output:
Apple
Banana
Mango
๐น 6. The "while" Loop โญ
A "while" loop continues executing as long as the condition remains True.
Syntax
while condition:
# Code
Example
count = 1
while count <= 5:
print(count)
count += 1
Output:
1 2 3 4 5๐น 7. Infinite Loop
Be careful when using "while" loops.
while True:
print("Hello")
This loop never stops unless interrupted.
Always ensure the condition eventually becomes False.
๐น 8. Loop Control Statements โญ
"break" - Stops the loop immediately
for i in range(10):
if i == 5:
break
print(i)
Output:
0 1 2 3 4"continue" - Skips the current iteration
for i in range(5):
if i == 2:
continue
print(i)
Output:
0 1 3 4"pass" - Acts as a placeholder
for i in range(5):
pass
Useful when writing incomplete code.
๐น 9. Nested Loops
A loop inside another loop.
for i in range(3):
for j in range(2):
print(i, j)
Output:
0 0
0 1
1 0
1 1
2 0
2 1
๐น 10. Real-World Data Science Example
Calculate the total sales.
โค4๐1
sales = [1000, 2000, 1500, 3000]
total = 0
for amount in sales:
total += amount
print(total)
Output:
7500๐น 11. Common Mistakes
โ Forgetting to update the loop variable
count = 1
while count <= 5:
print(count)
This creates an infinite loop because
count never changes.Correct:
count = 1
while count <= 5:
print(count)
count += 1
๐ฏ Practice Questions
1. Print numbers from 1 to 10 using a "for" loop
2. Print even numbers from 2 to 20
3. Find the sum of numbers from 1 to 100
4. Print all elements of a list using a loop
5. Create a multiplication table of any number using a "for" loop
๐ฏ Key Takeaways
โ Use a "for" loop when the number of iterations is known
โ Use a "while" loop when the number of iterations depends on a condition
โ range() generates sequences of numbers
โ break exits the loop immediately
โ continue skips the current iteration
โ pass acts as a placeholder
Loops are one of the most important concepts in Python. You'll use them extensively for data processing, feature engineering, machine learning, automation, and solving coding interview questions.
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Which loop is generally used when you know the number of iterations in advance?
Anonymous Quiz
17%
A) while loop
60%
B) for loop
16%
C) do-while loop
7%
D) Infinite loop
โค3
Which keyword is used to immediately terminate a loop?
Anonymous Quiz
7%
A) continue
8%
B) pass
78%
C) break
7%
D) exit
โค2
Which statement about the while loop is correct?
Anonymous Quiz
3%
A) It always runs exactly 10 times.
7%
B) It executes only once.
86%
C) It continues executing as long as the condition is True.
3%
D) It can only be used with lists.
โค3
What is the output of the following code?
total = 0
for i in range(1, 4): total += i print(total)
total = 0
for i in range(1, 4): total += i print(total)
Anonymous Quiz
22%
3
36%
6
27%
10
15%
5
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๐ Data Science Roadmap 2026
๐ Phase 1: Programming Fundamentals
๐ Topic 6: Python Functions
So far, you've learned variables, operators, input/output, conditional statements, and loops. As your programs grow larger, writing the same code repeatedly becomes inefficient. That's where functions come in.
A function is a reusable block of code that performs a specific task. Functions make your code cleaner, easier to maintain, and reusable.
Functions are heavily used in Data Science, Machine Learning, and AI because they allow you to organize complex workflows into smaller, manageable pieces.
๐น 1. What is a Function?
A function is a named block of code that executes only when it is called.
Instead of writing the same logic multiple times, you write it once inside a function and reuse it whenever needed.
Example
Output
๐น 2. Why Do We Use Functions?
Functions help you:
โ Avoid writing duplicate code
โ Improve code readability
โ Make debugging easier
โ Reuse code in multiple places
โ Build modular applications
๐น 3. Defining a Function
Syntax
Example:
๐น 4. Function Parameters
Parameters allow you to pass information into a function.
Output
Here, "name" is called a parameter.
๐น 5. Function Arguments
When calling a function, the values you pass are called arguments.
Output
Here:
โข "number" โ Parameter
โข "5" โ Argument
๐น 6. Returning Values
A function can return a value using the return keyword.
Output
Using return allows the function's result to be stored or used later.
๐น 7. Default Parameters
You can assign default values to parameters.
Output
๐น 8. Multiple Return Values
A function can return more than one value.
Output
๐น 9. Scope of Variables
Variables created inside a function are called local variables.
Trying to access
outside the function will produce an error because it exists only inside the function.
๐น 10. Built-in Functions
Python provides many ready-to-use functions.
Examples:
Output
๐น 11. Real-World Data Science Example
Calculate the average marks of students.
Output
Functions like this are commonly used while cleaning data, calculating statistics, and building machine learning pipelines.
๐น 12. Common Mistakes
โ Forgetting to Call the Function
Correct:
โ Forgetting to Return a Value
๐ฏ Practice Questions
1. Write a function to add two numbers.
2. Create a function to calculate the square of a number.
3. Write a function that checks whether a number is even or odd.
4. Create a function to calculate the average of a list.
5. Write a function that returns the largest of three numbers.
Double Tap โค๏ธ For Part-7
๐ Phase 1: Programming Fundamentals
๐ Topic 6: Python Functions
So far, you've learned variables, operators, input/output, conditional statements, and loops. As your programs grow larger, writing the same code repeatedly becomes inefficient. That's where functions come in.
A function is a reusable block of code that performs a specific task. Functions make your code cleaner, easier to maintain, and reusable.
Functions are heavily used in Data Science, Machine Learning, and AI because they allow you to organize complex workflows into smaller, manageable pieces.
๐น 1. What is a Function?
A function is a named block of code that executes only when it is called.
Instead of writing the same logic multiple times, you write it once inside a function and reuse it whenever needed.
Example
def greet():
print("Welcome to Data Science!")
greet()
Output
Welcome to Data Science!
๐น 2. Why Do We Use Functions?
Functions help you:
โ Avoid writing duplicate code
โ Improve code readability
โ Make debugging easier
โ Reuse code in multiple places
โ Build modular applications
๐น 3. Defining a Function
Syntax
def function_name():
# Function body
Example:
def welcome():
print("Hello, World!")
welcome()
๐น 4. Function Parameters
Parameters allow you to pass information into a function.
def greet(name):
print("Hello", name)
greet("Deepak")
Output
Hello Deepak
Here, "name" is called a parameter.
๐น 5. Function Arguments
When calling a function, the values you pass are called arguments.
def square(number):
print(number * number)
square(5)
Output
25
Here:
โข "number" โ Parameter
โข "5" โ Argument
๐น 6. Returning Values
A function can return a value using the return keyword.
def add(a, b):
return a + b
result = add(10, 20)
print(result)
Output
30
Using return allows the function's result to be stored or used later.
๐น 7. Default Parameters
You can assign default values to parameters.
def greet(name="Guest"):
print("Hello", name)
greet()
greet("Rahul")
Output
Hello Guest
Hello Rahul
๐น 8. Multiple Return Values
A function can return more than one value.
def calculate(a, b):
return a + b, a * b
sum_value, product = calculate(4, 5)
print(sum_value)
print(product)
Output
9
20
๐น 9. Scope of Variables
Variables created inside a function are called local variables.
def demo():
message = "Inside Function"
print(message)
demo()
Trying to access
message
outside the function will produce an error because it exists only inside the function.
๐น 10. Built-in Functions
Python provides many ready-to-use functions.
Examples:
numbers = [5, 2, 8, 1]
print(len(numbers))
print(max(numbers))
print(min(numbers))
print(sum(numbers))
Output
4
8
1
16
๐น 11. Real-World Data Science Example
Calculate the average marks of students.
def average(marks):
return sum(marks) / len(marks)
scores = [80, 75, 92, 88]
print(average(scores))
Output
83.75
Functions like this are commonly used while cleaning data, calculating statistics, and building machine learning pipelines.
๐น 12. Common Mistakes
โ Forgetting to Call the Function
def greet():
print("Hello")
# Nothing happens because the function isn't called.
Correct:
greet()
โ Forgetting to Return a Value
def add(a, b):
a + b
# Correct:
def add(a, b):
return a + b
๐ฏ Practice Questions
1. Write a function to add two numbers.
2. Create a function to calculate the square of a number.
3. Write a function that checks whether a number is even or odd.
4. Create a function to calculate the average of a list.
5. Write a function that returns the largest of three numbers.
Double Tap โค๏ธ For Part-7
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โค1
Which keyword is used to define a function in Python?
Anonymous Quiz
8%
A) function
84%
B) def
7%
C) func
1%
D) define
โค1
Which keyword is used to return a value from a function?
Anonymous Quiz
3%
A) break
12%
B) print
83%
C) return
2%
D) pass
โค1
Which of the following is a built-in Python function?
Anonymous Quiz
15%
A) calculate()
14%
B) average()
64%
C) sum()
7%
D) multiply()
โค2
What will be the output of the following code?
def multiply(a, b):
return a * b print(multiply(4, 5))
def multiply(a, b):
return a * b print(multiply(4, 5))
Anonymous Quiz
7%
9
93%
20
โค1๐ฅฐ1
What will be the output of the following code?
def greet(): print("Hello") greet()
def greet(): print("Hello") greet()
Anonymous Quiz
91%
Hello
9%
greet
โค3
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๐ Data Science Roadmap 2026
๐ Phase 1: Programming Fundamentals
๐ Topic 7: Python Data Structures (Lists, Tuples, Sets & Dictionaries)
Welcome back! ๐
So far, you've learned variables, operators, input/output, conditional statements, loops, and functions. Now it's time to learn one of the most important topics in Pythonโ Data Structures.
Data structures help us store, organize, and manage data efficiently. In Data Science, almost every dataset you work with will be stored or manipulated using these structures.
Python provides four built-in data structures:
โข List
โข Tuple
โข Set
โข Dictionary
Let's understand each one in detail.
๐น 1. List
A List is an ordered, mutable collection that allows duplicate values.
Creating a List
Output
Accessing Elements
Output
Modifying a List
Output
Adding Elements
Removing Elements
๐น 2. Tuple
A Tuple is an ordered collection that cannot be modified after creation (immutable).
Creating a Tuple
Accessing Elements
Output
Why Use Tuples?
Use tuples when your data should never change.
Examples:
โข Months of the year
โข Days of the week
โข Fixed coordinates
๐น 3. Set
A Set is an unordered collection of unique elements.
Duplicate values are automatically removed.
Creating a Set
Output
Adding Elements
Removing Elements
Common Uses
โข Remove duplicates
โข Membership testing
โข Mathematical set operations
๐น 4. Dictionary โญ
A Dictionary stores data as key-value pairs.
It is one of the most frequently used data structures in Data Science.
Creating a Dictionary
Accessing Values
Output
Adding a New Key
Updating a Value
Removing a Key
๐น 5. Comparison of Data Structures
Feature | List | Tuple | Set | Dictionary
Ordered | โ | โ | โ | โ
Mutable | โ | โ | โ | โ
Duplicates Allowed | โ | โ | โ | Keys โ
Indexed | โ | โ | โ | By Key
๐น 6. Common List Methods
๐น 7. Common Dictionary Methods
๐ Phase 1: Programming Fundamentals
๐ Topic 7: Python Data Structures (Lists, Tuples, Sets & Dictionaries)
Welcome back! ๐
So far, you've learned variables, operators, input/output, conditional statements, loops, and functions. Now it's time to learn one of the most important topics in Pythonโ Data Structures.
Data structures help us store, organize, and manage data efficiently. In Data Science, almost every dataset you work with will be stored or manipulated using these structures.
Python provides four built-in data structures:
โข List
โข Tuple
โข Set
โข Dictionary
Let's understand each one in detail.
๐น 1. List
A List is an ordered, mutable collection that allows duplicate values.
Creating a List
fruits = ["Apple", "Banana", "Mango"]
print(fruits)
Output
['Apple', 'Banana', 'Mango']
Accessing Elements
print(fruits[0])
print(fruits[2])
Output
Apple
Mango
Modifying a List
fruits[1] = "Orange"
print(fruits)
Output
['Apple', 'Orange', 'Mango']
Adding Elements
fruits.append("Grapes")
print(fruits)Removing Elements
fruits.remove("Orange")
print(fruits)๐น 2. Tuple
A Tuple is an ordered collection that cannot be modified after creation (immutable).
Creating a Tuple
colors = ("Red", "Green", "Blue")
print(colors)Accessing Elements
print(colors[1])
Output
Green
Why Use Tuples?
Use tuples when your data should never change.
Examples:
โข Months of the year
โข Days of the week
โข Fixed coordinates
๐น 3. Set
A Set is an unordered collection of unique elements.
Duplicate values are automatically removed.
Creating a Set
numbers = {1, 2, 2, 3, 4, 4, 5}
print(numbers)Output
{1, 2, 3, 4, 5}Adding Elements
numbers.add(6)
Removing Elements
numbers.remove(3)
Common Uses
โข Remove duplicates
โข Membership testing
โข Mathematical set operations
๐น 4. Dictionary โญ
A Dictionary stores data as key-value pairs.
It is one of the most frequently used data structures in Data Science.
Creating a Dictionary
student = {
"name": "Deepak",
"age": 24,
"course": "Data Science"
}
print(student)Accessing Values
print(student["name"])
Output
Deepak
Adding a New Key
student["city"] = "Mumbai"
Updating a Value
student["age"] = 25
Removing a Key
del student["course"]
๐น 5. Comparison of Data Structures
Feature | List | Tuple | Set | Dictionary
Ordered | โ | โ | โ | โ
Mutable | โ | โ | โ | โ
Duplicates Allowed | โ | โ | โ | Keys โ
Indexed | โ | โ | โ | By Key
๐น 6. Common List Methods
numbers = [10, 20, 30]
numbers.append(40)
numbers.insert(1, 15)
numbers.remove(20)
numbers.sort()
print(numbers)
๐น 7. Common Dictionary Methods
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