CS21: Quiz 2 Study Guide

In addition to all concepts from Quiz 1…

You should be able to define the following terms:

• data types: integer, float, string, boolean, list
• branching and looping
• the Accumulator design pattern
• string indexing

You should understand and be able to use the following Python concepts:

• basic for loops
• range()
• basic arithmetic expressions using +, -, *, /, //, **, %
• conversion between the int, float, and str types
• the empty string ""
• string concatenation with +, string repetition with *
• string indexing with []
• for loops over strings
• len()
• tracing a program (show the output)
• if, if/else, if/elif/else
• the relational operators <, <=, ==, >, >=, !=
• the boolean operators and, or, and not
• nested statements (e.g., nested if statements, if/else in a loop; etc)
• print formatting
• accumulator pattern using string, float, or int variables
• string comparisons
• ord() and chr()

Practice problems:

1. Show the output from the following code fragments:

for i in range(4):
      print(i)
      print("--")

for x in range(6):
      print(x, x**2)
print("done!")

text = "hello!"
for i in range(len(text)):
      print("-" + text[i] + "-")

2. Write a program that asks the user for their name, and then prints their name 20 times.

3. Given these assignments:

x = 5
y = 13
S = "we love computer science"

Show the value and type of each expression below:

x < 10 and y < 10
x < 10 or y < 10
x < 10 and x > 0
x > 10 or x < 0
(5/x) > 7.0
len(S) >= 10
S[0] < S[1]

4. Trace the following program and show it’s output:

x = 3
print("%d  %d" % (0,x))
for i in range(5):
    if x % 2 == 0:
        x = x / 2
    else:
        x = (3*x+1)/2
    print("%d  %d" % (i,x))

5. Write a program that asks the user how many grades they want to average, reads in those grades and prints their average.

Enter number of grades to average: 5

Enter grade: 96
Enter grade: 86
Enter grade: 76
Enter grade: 66
Enter grade: 56

Average is: 76.0