Relational, Logical & Identity Operators Practice

Instructions

Programs make decisions by asking questions that have a True or False answer. Python has three groups of operators for asking these questions. Every expression below produces a Boolean value: True or False.

1. Relational (comparison) operators

Relational operators compare two values. In the examples below, x = 7.

• = and == are different. One = stores a value in a variable. Two == compare two values.
• Watch the boundary. "18 or older" includes 18, so it is >= 18. "Over 18" does not include 18, so it is > 18.
• The = always comes second: write >= and <=, never => or =<.
• Text comparisons are case-sensitive. "Maya" == "maya" is False.
• Ints and floats compare by value. 5 == 5.0 is True.

2. Logical operators: and, or, not

Logical operators combine or flip True/False values. They are lowercase English words in Python (not &&, || or ! like some other languages).

age = 15
print(age >= 13 and age <= 19)  # True

3. Identity operators: is, is not

== asks "do these have the same value?" is asks "are these the very same object in memory?" is not asks the opposite.

a = [1, 2]
b = a           # b points to the SAME list as a
c = [1, 2]      # c is a NEW list with the same values
print(a == c)   # True   same values
print(a is c)   # False  different objects
print(a is b)   # True   same object

• The most common use of is is checking for None. The official Python style guide (PEP 8) says to write x is None or x is not None, not x == None.
• Do not use is to compare numbers or text. Use == for those. Python may even show a SyntaxWarning if you write something like x is 5.
• is not is two words with a space between them.

4. Order: which part does Python do first?

When operators are mixed, Python works in this order: (1) comparisons such as ==, <, is, then (2) not, then (3) and, then (4) or. Parentheses always go first, so use them to make your meaning clear.

print(True or False and False)     # True   and goes first: True or (False and False)
print((True or False) and False)   # False  parentheses change the order

How this works

1. Enter your first name, last name initial, and class period, then click Start Assignment. Your start time is recorded.
2. The assignment opens in a Python editor with three files (tabs) and 30 problems. Complete every orange dashed box and drop down.
3. Click ▶ Run on any part to see what Python would print in the terminal. Run does not grade you, so check your work carefully.
4. When you finish all three tabs, click Submit for Score. Your end time is recorded and your score appears. Answers cannot be changed after submitting.

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