Python: Logic type
In addition to arithmetic operations, there are also comparison operations in mathematics, such as
5 > 4 or
3 < 1. They also exist in programming. For example, when we go to a website, the username and password are compared with those in the database. If they are, they let us in; they authenticate us. In this lesson, we'll get to know more about comparison operations.
Programming languages have adapted all mathematical comparison operations unchanged, except for the equality and inequality operators. In mathematics, we use the
= sign, but in programming, this is quite rare.
In many languages, the symbol
= is used to assign values to variables. That's why in Python, we use
== for comparison.
List of comparison operations:
<— less than
<=— less than or equal to
>— more than
>=— greater than or equal to
==— equal to
!=— not equal to
These operations apply not only to numbers. For example, you can use the equality operator to compare strings:
password == text is a comparison of the value of strings that are written in different variables.
A logical operation like
5 > 4 or
password == text is an expression. Its result is the special value
False. This is a new data type for us -
result = 5 > 4 print(result) # => True print('one' != 'one') # => False
Along with strings (
str) and integers and rational numbers, the
bool type is one of Python's primitive data types.
Let's try to write a simple function that takes the age of a child as input and determines whether the child is a baby or not. Babies are defined as children under one year old:
def is_infant(age): return age < 1 print(is_infant(3)) # => False
Any operation is an expression, so the only line of the function we write is “return the value that results from the comparison
age < 1”. Depending on the argument passed, the comparison will be
return will return that result.
Now, perform the check on a child who's six months old:
print(is_infant(0.5)) # => True
The result of the
True operation. So the child is definitely a baby.
Write a function
is_pensioner() that takes someone's age as a single argument and checks whether that person is at retirement age. For the purposes of this exercise, retirement age is considered to be 60 years or over.
is_pensioner(75) # True is_pensioner(18) # False
The exercise doesn't pass checking. What to do? 😶
If you've reached a deadlock it's time to ask your question in the «Discussions». How ask a question correctly:
- Be sure to attach the test output, without it it's almost impossible to figure out what went wrong, even if you show your code. It's complicated for developers to execute code in their heads, but having a mistake before their eyes most probably will be helpful.
In my environment the code works, but not here 🤨
Tests are designed so that they test the solution in different ways and against different data. Often the solution works with one kind of input data but doesn't work with others. Check the «Tests» tab to figure this out, you can find hints at the error output.
My code is different from the teacher's one 🤔
It's fine. 🙆 One task in programming can be solved in many different ways. If your code passed all tests, it complies with the task conditions.
In some rare cases, the solution may be adjusted to the tests, but this can be seen immediately.
I've read the lessons but nothing is clear 🙄
It's hard to make educational materials that will suit everyone. We do our best but there is always something to improve. If you see a material that is not clear to you, describe the problem in “Discussions”. It will be great if you'll write unclear points in the question form. Usually, we need a few days for corrections.
By the way, you can participate in courses improvement. There is a link below to the lessons course code which you can edit right in your browser.
“Logic type (bool)” a data type with two possible values: