Grade 10 Computer Science — Going through a file line by line

Follow a loop that visits every line of a file in turn, turns each line into a number where it needs to, and leaves a total or a count behind.

Name: ________________________

1.A decision inside this loop lets only some of the lines reach the counter. What does the program print?

f = open("sales.txt", "w")
f.write("12\n30\n5\n22\n")
f.close()
big = 0
f = open("sales.txt", "r")
for line in f:
    if int(line) > 20:
        big = big + 1
f.close()
print(big)

2.A program adds up the numbers in a file, one line at a time. Someone then adds one more line to the file, holding 5, and the program is run again without being changed. What is different?
- a) The loop makes one more trip, and the total is 5 larger
- b) The total is 5 larger, but the loop makes the same number of trips as before
- c) Nothing, because the program was not changed
- d) The loop makes one more trip, and the total is 1 larger

3.This loop keeps hold of the largest number it has seen so far. What does the program print?

f = open("temps.txt", "w")
f.write("14\n39\n22\n")
f.close()
best = 0
f = open("temps.txt", "r")
for line in f:
    if int(line) > best:
        best = int(line)
f.close()
print(best)

4.The numbers saved in this file are added up as the loop meets them. What does the program print?

f = open("marks.txt", "w")
f.write("8\n3\n6\n")
f.close()
total = 0
f = open("marks.txt", "r")
for line in f:
    total = total + int(line)
f.close()
print(total)

5.This loop prints as it goes rather than keeping anything back. What is the last number it prints?

f = open("steps.txt", "w")
f.write("3\n5\n2\n")
f.close()
f = open("steps.txt", "r")
for line in f:
    print(int(line) * 10)
f.close()

6.A program opens a file, goes through it with a line loop, and closes it again. Sort each of these lines of code by how often it runs.
Groups: Runs once, outside the loop · Runs once for every line in the file
- print(total)
- print(int(line) * 2)
- f.close()
- f = open("data.txt", "r")
- total = 0
- total = total + int(line)

7.The file this loop is given has nothing written in it at all. What does the program print?

f = open("empty.txt", "w")
f.write("")
f.close()
total = 0
f = open("empty.txt", "r")
for line in f:
    total = total + int(line)
f.close()
print(total)

8.Nothing in these lines is a number, and the loop does not try to make one. What does the program print?

f = open("shades.txt", "w")
f.write("red\ngreen\nblue\nblack\n")
f.close()
count = 0
f = open("shades.txt", "r")
for line in f:
    count = count + 1
f.close()
print(count)

Answer key — Grade 10 Computer Science — Going through a file line by line

1. 2
2. a) The loop makes one more trip, and the total is 5 larger
3. 39
4. 17
5. 20
6. f = open("data.txt", "r") → Runs once, outside the loop; total = 0 → Runs once, outside the loop; total = total + int(line) → Runs once for every line in the file; print(int(line) * 2) → Runs once for every line in the file; f.close() → Runs once, outside the loop; print(total) → Runs once, outside the loop
7. 0
8. 4