python Day3

Python Conditions and If statements:

• Python supports the usual logical conditions from mathematics:

1. Equals: a == b
2. Not Equals: a != b
3. Less than: a < b
4. Less than or equal to: a <= b
5. Greater than: a > b
6. Greater than or equal to: a >= b

• These conditions can be used in several ways, most commonly in "if statements" and loops.

• An "if statement" is written by using the if keyword.

• The if statement evaluates a condition (an expression that results in True or False).

• If the condition is true, the code block inside the if statement is executed.

• If the condition is false, the code block is skipped.

1.IF STATEMENT:

a = 33
b = 200

if b > a:
  print("b is greater than a")

OUTPUT:

b is greater than a

2.Multiple Statements in If Block

• Multiple statements inside an if block. All statements must be indented at the same level.

Example

• Multiple statements in an if block:

age = 20
if age >= 18:
  print("You are an adult")
  print("You can vote")
  print("You have full legal rights")

OUTPUT:

You are an adult
You can vote
You have full legal rights

3.Python Elif Statement

• The elif keyword is Python's way of saying "if the previous conditions were not true, then try this condition".
• The elif keyword allows you to check multiple expressions for True and execute a block of code as soon as one of the conditions evaluates to True.

EXAMPLE:

a = 33
b = 33
if b > a:
  print("b is greater than a")
elif a == b:
  print("a and b are equal")

OUTPUT:
a and b are equal

4.Multiple Elif Statements:

• Many elif statements as you need. Python will check each condition in order and execute the first one that is true.

• Use elif when you have multiple mutually exclusive conditions to check.

• This is more efficient than using multiple separate if statements because Python stops checking once it finds a true condition.

Example
Testing multiple conditions:

score = 75

if score >= 90:
  print("Grade: A")
elif score >= 80:
  print("Grade: B")
elif score >= 70:
  print("Grade: C")
elif score >= 60:
  print("Grade: D")

OUTPUT:
Grade: C

5. Python Else Statement

• The else keyword catches anything which isn't caught by the preceding conditions.
• The else statement is executed when the if condition (and any elif conditions) evaluate to False.

a = 200
b = 33
if b > a:
  print("b is greater than a")
elif a == b:
  print("a and b are equal")
else:
  print("a is greater than b")

OUTPUT:
a is greater than b

6.Else Without Elif
How Else Works

• The else statement provides a default action when none of the previous conditions are true.
• Think of it as a "catch-all" for any scenario not covered by your if and elif statements.

Note: The else statement must come last. You cannot have an elif after an else.

• An else without the elif: Example

a = 200
b = 33
if b > a:
  print("b is greater than a")
else:
  print("b is not greater than a")

OUTPUT:

b is not greater than a

Complete If-Elif-Else Chain

• Combine if, elif, and else to create a comprehensive decision-making structure.

Example
7. Temperature classifier:

temperature = 22

if temperature > 30:
  print("It's hot outside!")
elif temperature > 20:
  print("It's warm outside")
elif temperature > 10:
  print("It's cool outside")
else:
  print("It's cold outside!")

OUTPUT:

It's warm outside