Basic Python: 6. Python Conditional Statements
Tags: python, beginners, programming, tutorial
Published: 2023-08-30 14:35:25

Conditional statements are an essential part of programming that allow you to control the flow of your code based on certain conditions. In Python, you can achieve this using `if`, `elif`, and `else` statements. These statements help your program make decisions and execute different blocks of code based on whether specific conditions are true or false.

### Table of Contents

1. **The `if` Statement**
2. **The `if-else` Statement**
3. **The `if-elif-else` Statement**
4. **Nested Conditional Statements**
5. **Ternary Operator**
6 **Combining Conditions**
7. **Using Logical Operators**

## 1. The `if` Statement

The `if` statement is used to execute a block of code only if a certain condition is true.

### Syntax:
```python
if condition:
    # Code to be executed if the condition is true
```

Here's a simple example that checks if a number is positive:

```python
num = 10

if num > 0:
    print("The number is positive")
```

## 2. The `if`-`else` Statement

The `if`-`else` statement allows you to execute one block of code when a condition is true, and another block when the condition is false.

### Syntax:
```python
if condition:
    # Code to be executed if the condition is true
else:
    # Code to be executed if the condition is false
```

Let's see an example that checks whether a number is even or odd:

```python
num = 7

if num % 2 == 0:
    print("The number is even")
else:
    print("The number is odd")
```

## 3. The `if`-`elif`-`else` Statement

The `if`-`elif`-`else` statement is used when you have multiple conditions to check. `elif` stands for "else if" and allows you to test multiple conditions in sequence.

### Syntax:
```python
if condition1:
    # Code to be executed if condition1 is true
elif condition2:
    # Code to be executed if condition2 is true
else:
    # Code to be executed if none of the conditions are true
```

Here's an example that categorizes a student's score into different grades:

```python
score = 85

if score >= 90:
    print("A")
elif score >= 80:
    print("B")
elif score >= 70:
    print("C")
else:
    print("F")
```

## 4. Nested Conditional Statements

You can also nest conditional statements within each other to handle more complex scenarios. Just be mindful of proper indentation to maintain code readability. Here's a basic example:

```python
x = 10
y = 5

if x > 0:
    if y > 0:
        print("Both x and y are positive")
    else:
        print("Only x is positive")
else:
    print("Neither x nor y is positive")
```

## 5. Ternary Operator
The ternary operator is a concise way to write simple if-else statements in a single line.
The ternary operator (`expression if condition else expression`) is a concise way to write conditional expressions.

```python
is_sunny = True
weather = "It's sunny!" if is_sunny else "It's cloudy."
print(weather)
```

## 6. Combining Conditions

You can combine conditions using logical operators `and`, `or`, and `not`.

```python
temperature = 25
is_raining = False
if temperature > 20 and not is_raining:
    print("Perfect weather for a picnic!")
```

## 7. Using Logical Operators

Logical operators help you build complex conditions by combining simpler ones.

```python
x = 10
y = 5
if x > 0 and y > 0:
    print("Both x and y are positive.")
elif x > 0 or y > 0:
    print("At least one of x or y is positive.")
else:
    print("Neither x nor y is positive.")
```