Erle Robotics Learning Python GitBook Free

Logical operators

Comparartors

Let's start with the simplest aspect of control flow: comparators. They are use to compare expressions.

Note that == compares whether two things are equal, and =assigns a value to a variable.

For example:

>>> 17 < 4
False
>>> 3 >= 1
True
>>> 40*2 == 40 +40
True
>>> 1**2 <= -1
False
>>>

Boolean Operators

and operator

and checks if both the statements are True.

True and True is True
True and False is False
False and True is False
False and False is False

Practice 1

Let's practice with and. Assign each variable to the appropriate boolean value.

• Set bool_one equal to the result ofFalse and False.
• Set bool_two equal to the result of -(-(-(-2))) == -2 and 4 >= 16**0.5.
• Set bool_three equal to the result of 19 % 4 != 300 / 10 / 10 and False.
• Set bool_four equal to the result of -(1**2) < 2**0 and 10 % 10 <= 20 - 10 * 2.
• Set bool_five equal to the result ofTrue and True.

You can check the results in your interpeter:

bool_one = False

bool_two = False

bool_three = False

bool_four = True

bool_five = True

or operator

orchecks if at least one of the statements is True.

True or True is True
True or False is True
False or True is True
False or False is False

Practice 2

Now do the same, but with the oroperator:

• Set bool_one equal to the result of 2**3 == 108 % 100 or 'Cleese' == 'King Arthur'.
• Setbool_two equalto the result of True or False.
• Set bool_three equal to the result of100**0.5 >= 50 or False.
• Set bool_fourequal to the result of True or True.
• Set bool_five equal to the result of1**100 == 100**1 or 3 * 2 * 1 != 3 + 2 + 1.

The result should be:

bool_one = True

bool_two = True

bool_three = False

bool_four = True

bool_five = False

not operator

not gives the opposite of the statemen.

Not True is False
Not False is True

Practice 6

Let's get some practice with not.

• Set bool_one equal to the result ofnot True.
• Set bool_two equal to the result of not 3**4 < 4**3.
• Set bool_three equal to the result of not 10 % 3 <= 10 % 2
• Set bool_four equal to the result of not 3**2 + 4**2 != 5**2.
• Set bool_five equal to the result of not not False.

The solution of this practice is:

bool_one = False

bool_two = True

bool_three = True

bool_four = True

bool_five = False

The order of operators

Boolean operators aren't just evaluated from left to right. Just like with arithmetic operators, there's an order of operations for boolean operators:

not is evaluated first; and is evaluated next; or is evaluated last.

Parentheses () ensure your expressions are evaluated in the order you want. Anything in parentheses is evaluated as its own unit.

Practice 4

Assign True or False as appropriate for bool_one through bool_five.

• Set bool_one equal to the result of False or not True and True.
• Set bool_two equal to the result of False and not True or True.
• Set bool_three equal to the result of True and not (False or False)
• Set bool_four equal to the result of not not True or False and not True.
• Set bool_five equal to the result of False or not (True and True).

The solution is the following one:

bool_one = False

bool_two = True

bool_three = True

bool_four = True

bool_five = False