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Logical Operators 1/2
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Course Content

Conditional Statements in Python

Logical Operators 1/2Logical Operators 1/2

Previously, we explored situations involving a single condition in the if statement. Now, let's delve into scenarios where we need to evaluate multiple conditions.

One approach is to use nested if statements, as demonstrated in the example:

Example 1:

However, relying heavily on nested if conditions is not considered best practice. A seasoned developer would prefer to use logical operators instead of nesting conditions.

Example 2:

Python language has 3 logical operators:

  1. and - condition_1 and condition_2 - works only if both conditions are True.
  2. or - condition_1 or condition_2 - works if at least one of the two specified conditions is True.
  3. not - not condition is applied to one condition (not two as above) and inverts its value.

In Python syntax, each "empty" value is equivalent to False, and any "non-empty" value is equivalent to True.

Example 3:

Let's continue by examining conditional statements with multiple conditions. Imagine you've taken exams in three subjects and received the following results: math_exam = 95, english_exam = 90, programming_exam = 100. You've decided to apply to three different universities, each with its own admission requirements. Let's explore these requirements.

To enter the first university, you must have a score greater than or equal to 90 in all three subjects simultaneously. Let's see if you meet this university's criteria.

As we can see, your scores from all exams are greater than or equal to 90, so our if statement worked.

Then move on to the next university. Here the condition is different, since this is the best university in your city, your scores must be greater than or equal to 95.

As we see that our condition is not fulfilled, since we have two objects that satisfy the condition, but the third object, namely english_exam = 90, it is less than 95. Therefore, we do not get anything as a result, and our if statement is not executed.

Moving on to the next university. Here the condition is quite simple. In order to pass here, you need to have at least one subject that has passed 100 points.

It is obvious that for this case we need to use the or operator.

As we can see, we still have one subject with a score of 100. It's important to note that for the or operator, it's enough for just one condition to be True.

It's worth remembering that if none of the conditions are True, the if statement won't be executed, and you won't meet the criteria.

Now, it's time to practice!

Everything was clear?

Section 1. Chapter 5