Python If, If-Else Statements Tutorial
Tags: python, tutorial, programming, beginners
Published: 2023-02-23 15:11:36

## [Python if statement](https://www.programdoc.com/python/if-else)

In Python, `if` statement is used for conditional execution of code based on certain conditions.

The syntax for the `if` statement
```py
if condition:
    # code to execute if condition is true
``` 

Here, the `condition` is a boolean expression that can be evaluated to `True` or `False`. If the condition is true, then the code inside the `if` statement is executed.

```py
## Check if a number is positive
num = 5

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

Output:
`The number is positive` 

In the above example, the value of `num` is checked to see if it is greater than `0`. If the condition is true, then the message "The number is positive" is printed.

```py
## Check if a number is even or odd
num = 4

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

Output:
`The number is even` 

In this example, the value of `num` is checked to see if it is even or odd. If the number is divisible by `2` (i.e. `num % 2 == 0`), then it is even and the message "The number is even" is printed. Otherwise, the number is odd and the message "The number is odd" is printed.

The `else` keyword is used here to provide an alternative code block to be executed if the condition in the `if` statement is false.

That's it! This is how you can use `if` statement in Python to execute code based on certain conditions.



## Python If-Else Statements

In Python, the `if-else` statement is used to execute a code block based on a condition.

The basic syntax of `if-else` statement is as follows:

```py
if condition:
    # execute this block if the condition is true
else:
    # execute this block if the condition is false
``` 

Here's an example that uses an `if-else` statement to check if a number is positive or negative:

```py
# Check Positive or Negative
num = int(input("Enter a number: "))

if num >= 0:
    print("The number is positive or zero")
else:
    print("The number is negative")
``` 

Output:
```py
Enter a number: 5
The number is positive or zero
``` 

In this example, if the value of `num` is greater than or equal to zero, the program prints "The number is positive or zero." If the value of `num` is less than zero, the program prints "The number is negative."

Here's another example that uses nested `if-else` statements to check a student's grade:

```py
# Find Student Grade
marks = int(input("Enter the marks obtained: "))

if marks >= 90:
    grade = "A+"
elif marks >= 80:
    grade = "A"
elif marks >= 70:
    grade = "B"
elif marks >= 60:
    grade = "C"
elif marks >= 50:
    grade = "D"
else:
    grade = "F"

print("The grade obtained is", grade)
``` 

Output:
```py
Enter the marks obtained: 92
The grade obtained is A+
``` 
if statement `marks >= 90` is true for  value 92

In this example, the program first checks if the `marks` are greater than or equal to 90. If they are, it assigns the value "A+" to the variable `grade`. If not, it checks if the `marks` are greater than or equal to 80, and so on. If the `marks` are less than 50, the program assigns the value "F" to the variable `grade`.


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