Python Logic & Structure Practice

Instructions

1. Instructions run from top to bottom

A Python program is a list of instructions. Python runs them one at a time, from the top line to the bottom line. Each instruction goes on its own line.

print("First")     # runs 1st
print("Second")    # runs 2nd
print("Third")     # runs 3rd

Because Python reads from the top down, a variable must be created before you use it.

name = "Ava"
print(name)    # prints Ava

print(name)    # Error! name does not exist yet
name = "Ava"

Two more rules for writing instructions:

• Python is case sensitive. print works, but Print does not.
• Every opening parenthesis ( needs a closing parenthesis ).

2. Comments

A comment starts with #. Python ignores everything from the # to the end of that line. Programmers use comments to explain code to people.

• Full-line comment: the whole line starts with #, so the whole line is skipped.
• Inline comment: code comes first, then #. The code runs, and only the part after # is skipped.
• Commenting out code: putting # in front of a line of code turns it off without deleting it.
• Careful: a # inside quotes, like "#1 fan", is part of the text, not a comment.

3. Indentation

Indentation means spaces at the start of a line. Python pays close attention to these spaces. Later in the course you will learn when to indent. For now, the rule is simple: every line starts at the left edge, with no spaces in front.

On this page, each orange dot · stands for one space.

name = "Ava"
print(name)

name = "Ava"
··print(name)    # 2 extra spaces

Spaces in the middle of a line, like x = 5, do not cause an error. Only spaces at the start do. (Style tip: one space on each side of =, like x = 5, is easiest to read.)

Error messages you may see in the terminal

• IndentationError: unexpected indent means a line has extra spaces at the start.
• NameError: name 'name' is not defined means a variable was used before it was created, or a word was spelled wrong (like Print).
• SyntaxError: '(' was never closed means a closing parenthesis ) is missing.

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 four files (tabs). 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 four tabs, click Submit for Score. Your end time is recorded and your score appears. Answers cannot be changed after submitting.

Student Information