for Loops & range() Practice

Instructions

Quick review

range(5)          # 0 1 2 3 4
range(1, 6)       # 1 2 3 4 5
range(2, 11, 2)   # 2 4 6 8 10
range(5, 0, -1)   # 5 4 3 2 1

for letter in "hey":
    print(letter)
pets = ["dog", "cat"]
for pet in pets:
    print(pet)

"a" in "cat"              # True
"kiwi" in ["kiwi", "fig"]  # True
"ki" in ["kiwi", "fig"]    # False
"x" not in "cat"          # True

• A for loop repeats once for every item in a sequence. The loop variable holds the next item each time.
• In range(start, stop, step), start is in, stop is out. The default start is 0 and the default step is 1. To include the last number, add 1 to the stop: range(1, 11) gives 1 to 10.
• To count down, use a negative step and a stop that is smaller than the start: range(10, 0, -1).
• A string loop visits one character at a time (spaces count too). A list loop visits one whole item at a time. Lists use square brackets and commas: ["apple", "kiwi"].
• in answers True or False. In a string it can find a letter or a chunk. In a list it needs a whole item. It is case sensitive.
• print(x, end=" ") keeps the output on the same line. A plain print() ends the line.

Error messages you may see in the terminal

• SyntaxError: expected ':' means the for line is missing its colon.
• IndentationError: expected an indented block after 'for' statement on line 3 means the body is not indented 4 spaces.
• TypeError: 'int' object is not iterable means you tried for i in 5:. Use range(5).
• ValueError: range() arg 3 must not be zero means the step is 0.
• TypeError: 'in <string>' requires string as left operand, not int means you checked for a number inside a string. Put quotes around it.
• No error at all is possible too! Off-by-one ranges and a countdown with a positive step run without an error but give the wrong output. Compare your output with the expected output.

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). Each orange numbered box or drop down is one practice item. There are 20 items.
3. Click ▶ Run on Parts 1 to 3 to see what Python prints. Compare it with the expected output. Run is turned off for Part 4. 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