Skip to content

Comparisons & Logical operators

Comparisons

Now, that we have covered all basic Python types, we can start comparing them. As the name suggests, comparisons are used to compare two values. The result of a comparison is a boolean value.

Equality

print("Abc" == "abc")
>>> Output
False

We can compare any type with each other. In the above case, the comparison checks if both strings are equal, using the == operator. The result is False, because the case of the strings do not match.

Let's check if two integers are equal:

print(1 == 1)
>>> Output
True

Inequality

We can also check if two values are not equal with the != operator:

user_name = "Eric"
print(user_name != "admin")
>>> Output
True

print(2 != 2.1)
print(2 != 2)
>>> Output
True
False

Numerical comparisons

... are done with:

Operator Description
< less than
> greater than
<= less than or equal
>= greater than or equal 
print(1 < 2)
print(1 > 2)
>>> Output
True
False

print(10.2 <= 10.2)
print(9.99 >= 10)
>>> Output
True
False

Logical Operators

You may want to check multiple conditions at the same time. For example, sometimes you might need two conditions to evaluate to True in order to perform an action. Hence, logical operators are introduced. There are three logical operators:

Operator Meaning Example Result
and Returns True if both statements are True True and True True
or Returns True if one of the statements is True True or False True
not Reverses a result not True False

and

age = 20
print(age >= 18 and age <= 25) # True and True -> True
>>> Output
True

or

age = 20
print(age >= 50 or age <= 25) # False or True -> True
>>> Output
True

not

age = 20
print(not(age >= 18)) # not(True) -> False
>>> Output
False
Evaluate password security requirements: Part 1

Secure lock

You are given two variables that describe properties of a password:

  • password_length - represents how many characters are in the password (int)
  • has_special_characters - represents whether the password contains special characters (True/False)

Variables to use:

password_length = 18
has_special_characters = False

Task:

Write code that checks if this password is secure based on these requirements:

  1. The password must be longer than 10 characters
  2. The password must contain special characters

Use comparisons and logical operators to create a single expression that evaluates whether BOTH requirements are met.

Evaluate password security requirements: Part 2

To increase security, a third variable is introduced alongside the previous password properties:

already_used - represents whether this password has been used before (True/False)

Variables to use:

password_length = 18
has_special_characters = True
already_used = False

Task:

Write code that checks if this password is secure based on these three requirements:

  1. The password must be longer than 10 characters
  2. The password must contain special characters
  3. The password must not have been used before

Build on your previous solution and evaluate whether all THREE requirements are met.

Recap

We have covered the basic comparison and logical operators in Python .

  • Comparisons

    • == for equality
    • != for inequality
    • <, >, <=, >= for numerical comparisons

  • Logical operators

    • and
    • or
    • not