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Learning Python and Its Operators: A Beginner's Guide
The and operator in Python accepts two operands, which can be either Boolean expressions or objects, or a combination of the two. In conjunction with those operands, the and operator constructs more complex expressions. The operands of a and expression are referred to as conditions in most cases. If both of the requirements are met, then the and expression delivers a true result for the condition. If this is not the case, it produces a false result:


>>> The truth and nothing but the truth

True

 

>>> The terms false and false are used interchangeably.

False

 

>>> True or False statements

False

 

>>> The terms False and True

False

These examples demonstrate that a and expression only returns True when both operands in the expressions are true, as demonstrated in the previous section. Because the and operator requires two operands to construct an expression, it is referred to as a binary operator.

 

The following are some short instances of what is known as the and operator's truth table:

 

operand1 operand2 operand1 and operand2 operand1 and operand2

True True True

True False False

False False False

False True False

This table illustrates the truth value of a Boolean expression, such as operand1 and operand2, when both operands are true. The truth values of the operands have an impact on the outcome of the expression's result. It will be true if and only if both of these conditions are met. Otherwise, the result will be false. This is the general reasoning that underpins the use of the and operator. In Python, however, this operator can perform a variety of additional operations.

 

In the next sections, you'll learn how to use different types of operands and how to construct your own expressions using them.

 

With the help of Python's and operator, we can create Boolean expressions.

You'll often utilize logical operators to construct compound Boolean expressions, which are combinations of variables and values that result in a Boolean value as a result of the operation performed. In other words, Boolean expressions yield either True or False depending on the condition.

 

Comparisons and equality tests are two instances of this type of phrase that are frequently encountered:

 

>>> 5 = 3 + 2 = 5.

True

>>> 5 > 3 >>> 5 > 3

True

>>> 5 3 (five and three)

False

>>> 5!= 3!= 5!= 3

True

 

>>> [5, 3] == [5, 3] >>> [5, 3] == [5, 3]

True

 

>>> "hey" is the same as "hello."

False

All of these expressions return either True or False, indicating that they are Boolean expressions in nature. You can use the and keyword to combine them to build compound expressions that test two or more subexpressions at the same time:

 

>>> 5 is greater than 3 and 5 equals 3 plus 2

True

 

>>> 5 x 3 and 5 x 5 equals 5

False

 

>>> 5 == 5, and 5!= 5, respectively.

False

 

>>> 5 3 and 5!= 5 are two different ways of saying the same thing.

False

The result of combining two True expressions is also True in this case, as seen below. Any other combination results in a False result. From the above examples, you can infer that the following is the syntax for generating compound Boolean statements with the and operator:

 

expression1 and expression2 are two expressions

Similarly, if both of the subexpressions expression1 and expression2 evaluate to True, then the compound expression evaluates to True. If at least one of the subexpressions evaluates to False, then the result is False as a whole.

 

When constructing a compound expression, there is no restriction on the amount of and operators that can be used together. This means that you can use the following operators to combine more than two subexpressions in a single expression: multiple and operators

 

>>> 5 > 3 and 5 == 3 + 2 and 5!= 3 >>> 5 > 3 and 5 == 3 + 2 and 5!= 3

True

 

> 5 x 3 and 5 == 3 and 5!= 3 and 5!= 3

False

Once again, if all of the subexpressions evaluate to True, you will get the answer True. If you don't, you'll get False. It's important to remember that Python evaluates expressions sequentially from left to right, which becomes especially important as expressions grow in length.

 

 

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Preventing the Evaluation from Taking Place

In Python, the logical operators and and or make advantage of a technique known as short-circuit evaluation, also known as lazy evaluation. To put it another way, Python only evaluates the operand on the right when it is absolutely necessary.

 

Python begins by evaluating the left operand of a and expression in order to determine the final outcome of the expression. It follows that the entire phrase is false if this condition is not met. In this case, there is no need to evaluate the operand on the right side of the equation. Python is already aware of the eventual outcome.

 

The presence of a false left operand immediately results in the expression being false as a whole. In order to evaluate the remaining operand, it would be a waste of CPU time. Python avoids this from happening by interrupting the evaluation process.

 

However, the and operator evaluates the operand on the right only if both of the first operand's conditions are satisfied. In this situation, the truth value of the right operand has an impact on the ultimate result of the computation. If it is correct, then the entire expression is correct. If this is not the case, the phrase is false.

 

The following examples will help you better understand how this feature prevents short-circuiting.

 

>>> true func() is defined as follows:

... print("True func() is currently running")

... and the result is True

...

 

>>> def false func(): This function is defeated.

... print("Running false func()," "Running false func()")

... if the condition is met, return False

...

 

# true func() and false func() are used in Case 1 of this example.

True func is being used ()

False func is being used ()

False

 

false func() and true func() are two examples of case 2.

False func is being used ()

False

 

# Case 3: false func() and false func() are called.

False func is being used ()

False

 

> true func() and true func() # Case 4: true func()

True func is being used ()

True func is being used ()

True

The following is an explanation of how this code works:

 

Consider the following scenario: Python evaluates true func() and returns True. Python evaluates false func() and returns False as the final result in order to determine the ultimate outcome. You may verify this by looking at the output of both functions.

2. Python evaluates false func(), which yields False in this instance. The fact that Python already knows that the ultimate result is False means that true func will not be evaluated ().

Case 3: Python calls false func() and receives the value False as a response. It is not necessary to perform a second evaluation of the repeated function.

True is returned as a result of true func() being evaluated in Python in Case 4. The function is then re-evaluated by the program. Due to the fact that both operands evaluate to True, the final result is True as well.

Python works with Boolean expressions in a left-to-right fashion. Whenever it no longer needs to evaluate any additional operands or subexpressions in order to determine the ultimate output, it terminates itself. Remember that if the left operand of a and expression is false, then the right operand will not be evaluated.

 

The short-circuit assessment of your code can have a major impact on the performance of your code. Consider the following suggestions when creating structures and expressions in order to take advantage of this:

 

Time-consuming statements should be placed to the right of the and keyword. If the short-circuit rule is activated, the costly expression will not be executed in this manner.

The expression that is more likely to be false should be placed on the left side of the and keyword. By doing so, Python is more likely to be able to establish whether the entire expression is false by evaluating simply the left operand of the expression.

It is possible that you will want to avoid lazy evaluation in a specific Boolean expression at some point. You may accomplish this by employing the bitwise operators (&, |, and ). These operators are also used in Boolean expressions, but they evaluate the operands more quickly than the previous operators:

 

>>> true func() is defined as follows:

... print("True func() is currently running")

... and the result is True

...

 

>>> def false func(): This function is defeated.

... print("Running false func()," "Running false func()")

... if the condition is met, return False

...

 

>>> # Make use of logic and reasoning.

>>> false func() and true func() are two functions that can be used to test if a function is true or false ()

False func is being used ()

False

 

>>> # Make use of bitwise operations.

>>> false func() and true func() are two functions ()

False func is being used ()

True func is being used ()

False

As expected, the and operator performs a sluggish operation in the first expression. As a result of the first function's evaluation returning a false result, the second function is not evaluated by the program. The bitwise AND operator (&) in the second phrase, on the other hand, calls both procedures eagerly, despite the fact that the first function returns False. It should be noted that the end conclusion in both circumstances is False.

 

Despite the fact that this approach is effective, it is normally discouraged. When working with bits, you should use bitwise operators, and when working with Boolean values and expressions, you should use Boolean operators. More in-depth information on bitwise operators may be found in Bitwise Operators in Python (see Resources).

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