# Python Logical Operators: What is ‘&&’?

## Introduction

Python Logical Operators are used to perform logical operations on two or more conditions. These operators are used to evaluate whether a certain condition is true or not. The most commonly used logical operators in Python are AND, OR, and NOT. Using operators like AND in your Python code, you can make your programs more efficient and effective.

## What are Logical Operators?

In Python, logical operators are used to combine multiple conditions together and evaluate them as a single boolean expression. There are three types of logical operators in Python: and, or, and not.

The and operator returns True if both conditions it is evaluating are true, otherwise it returns False. For example:


x = 5
y = 10
if x > 0 and y > 0:
print("Both x and y are positive.")


In the above code block, the condition x > 0 and y > 0 are both true, so the statement “Both x and y are positive.” will be printed.

The or operator returns True if at least one of the conditions it is evaluating is true. For example:


x = 5
y = -10
if x > 0 or y > 0:
print("At least one of x or y is positive.")


In the above code block, the condition x > 0 is true even though y > 0 is false. Therefore, the statement “At least one of x or y is positive.” will be printed.

Finally, the not operator negates a boolean expression. That is, it returns True if its operand is false and vice versa. For example:


x = True
if not x:
print("x is false.")
else:
print("x is true.")


In the above code block, since x is initially set to True, the condition in the if statement evaluates to false (not True == False). Therefore, the statement “x is true.” will be printed.

## Python Logical Operators

Python Logical Operators are used to evaluate expressions and return a Boolean value. There are three logical operators in Python:

1. ‘and’ operator: This operator returns True if both the operands are True, otherwise, it returns False. For example:


x = 5
y = 10
if x > 0 and y < 20:
print("Both conditions are True")


In this example, both conditions x > 0 and y < 20 are True, so the output will be “Both conditions are True”. 2. ‘or’ operator: This operator returns True if at least one of the operands is True, otherwise, it returns False. For example:


x = 5
y = 10
if x == 4 or y == 10:
print("At least one condition is True")


In this example, the condition y == 10 is True, so the output will be “At least one condition is True”.

3. ‘not’ operator: This operator returns the opposite of the Boolean value of the operand. If the operand is True, it returns False and vice versa. For example:


x = 5
if not x == 4:
print("x is not equal to 4")


In this example, the condition x == 4 is False, so the output will be “x is not equal to 4”.

It is important to note that logical operators have a specific order of precedence in Python. ‘not’ has the highest precedence, followed by ‘and’, and then ‘or’. However, parentheses can be used to change the order of evaluation.

## The ‘and’ Operator

The ‘and’ operator is a logical operator in Python that returns True if both operands are True, otherwise it returns False. It takes two operands and the syntax for using the ‘and’ operator is:


operand1 and operand2


Let’s take a look at some examples:


# Example 1
x = 5
y = 10
if x > 0 and y < 15:
print("Both conditions are True")

# Output: Both conditions are True

# Example 2
x = 5
y = 20
if x > 0 and y < 15:
print("Both conditions are True")

# Output: Nothing is printed because the condition is False


In Example 1, both conditions are True, so the code inside the if statement is executed and “Both conditions are True” is printed. In Example 2, the second condition is False, so the code inside the if statement is not executed.

It’s important to note that the ‘and’ operator has higher precedence than the ‘or’ operator, which means that expressions with ‘and’ will be evaluated before expressions with ‘or’. You can use parentheses to change the order of evaluation if needed.

In summary, the ‘and’ operator is used to check if two conditions are both True. If both conditions are True, the expression evaluates to True. If one or both conditions are False, the expression evaluates to False.

## The ‘or’ Operator

In Python, the ‘or’ operator is used to combine two or more conditions in a logical expression. The resulting expression evaluates to True if at least one of the conditions is True.

Let’s take a look at an example:


x = 5
y = 10

if x < 3 or y > 9:
print("At least one condition is true")
else:
print("Both conditions are false")


In this example, the first condition (x < 3) is False, but the second condition (y > 9) is True. Since we’re using the ‘or’ operator, the entire expression evaluates to True and “At least one condition is true” is printed to the console.

It’s important to note that the ‘or’ operator short-circuits – that means that as soon as it finds a True condition, it stops evaluating any further conditions. This can be useful for optimizing code and preventing unnecessary computations.

## The ‘not’ Operator

In Python, the keyword ‘not’ is a logical operator that reverses the boolean value of an expression. It can be used with any expression that evaluates to True or False.

For example, let’s say we have a boolean variable ‘is_raining’ that is True if it’s currently raining and False otherwise. We can use the ‘not’ operator to check if it’s not raining:


is_raining = True
if not is_raining:
print("It's not raining!")
else:
print("It's raining.")


In this example, the ‘not’ operator reverses the boolean value of ‘is_raining’, so the code inside the ‘if’ statement will only execute if it’s not currently raining.

The ‘not’ operator can also be used with other expressions, such as comparisons:


x = 5
y = 10
if not x > y:
print("x is not greater than y.")
else:
print("x is greater than y.")


In this example, the ‘not’ operator reverses the result of the comparison ‘x > y’, so the code inside the ‘if’ statement will only execute if x is not greater than y.

Overall, the ‘not’ operator is useful for negating boolean values or comparison results in Python.

## ‘&&’ vs. ‘and’

In Python, logical operators are used to combine multiple conditions and return a Boolean value (True or False). The two most commonly used logical operators are ‘and’ and ‘or’. However, some programmers might be used to using ‘&&’ as a logical operator from other programming languages.

In Python, ‘&&’ is not a valid logical operator. Instead, the ‘and’ keyword should be used. The same goes for ‘||’, which is not valid in Python, and should be replaced with the ‘or’ keyword.

Here is an example of how to use the ‘and’ keyword in Python:


x = 5
y = 10
z = 15

if x < y and y < z:
print("Both conditions are True")
else:
print("At least one condition is False")


In this example, the ‘and’ keyword is used to combine two conditions: ‘x < y’ and ‘y < z’. Both conditions must evaluate to True in order for the code inside the if statement to execute. If at least one of the conditions is False, then the code inside the else statement will execute. It’s important to note that the ‘and’ keyword uses short-circuit evaluation. This means that if the first condition in an ‘and’ statement evaluates to False, then the second condition will not be evaluated because it’s already known that both conditions cannot be True. This can lead to more efficient code in certain situations. In summary, while some programmers might be used to using ‘&&’ as a logical operator from other programming languages, in Python it’s important to use the ‘and’ keyword instead.

## Conclusion

In conclusion, logical operators in Python are essential for creating complex conditions and controlling the flow of programs. The and and or operators are the most commonly used logical operators in Python, while the not operator is useful for negating conditions.

It is important to remember that the and and or operators use short-circuit evaluation, which means that they stop evaluating as soon as the result can be determined. This can have significant performance implications in certain situations.

It is also worth noting that the and operator in Python is equivalent to the && operator in other programming languages, while the or operator is equivalent to the || operator.

Overall, understanding logical operators is crucial for writing effective Python code and creating programs that behave as intended. With practice and experimentation, you can master these concepts and use them to write powerful and efficient Python programs.
Interested in learning more? Check out our Introduction to Python course!

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