Answers

F3.1 String handling

Strings, lists and records · GCSE · OCR J277 2.2.3, AQA 8525 3.2.8, Edexcel 1CP2 6.3.3 · about 15 min

What this lesson is about

Length, indexing, slicing, searching and joining strings, and f-strings.

• Joining strings
• Length and indexing
• Slicing
• Searching
• Building reports with f-strings

Questions 11 marks in all

1. [1 mark]What does this program print?

   first = "Bug"
   second = "Bot"
   print("Hello, " + first + second + ".")

   Answer:

   Hello, BugBot.

   + on strings joins them, and joining adds no spaces: the space is inside "Hello, ".

2. [1 mark]What happens with print("battery: " + 92)?

   1. ATypeError: text and a number cannot be joined with +
   2. BIt prints battery: 92
   3. CIt prints battery: + 92
   4. DSyntaxError
   Answer: A. Python will not join text and a number. Use str(92) or an f-string.

3. [1 mark]What does this program print?

   speed = 45
   print(f"driving at {speed} and half is {speed / 2}")

   Answer:

   driving at 45 and half is 22.5

   In an f-string, anything inside { } is worked out and dropped into the text.

4. [1 mark]What does this program print?

   word = "BugBot"
   print(len(word))
   print(word.upper())

   Answer:

   6
   BUGBOT

   len counts the characters, and upper gives the text in capitals.

5. [1 mark]What does this program print?

   print("-" * 5)

   Answer:

   -----

   Multiplying a string by a number repeats it.

6. [1 mark]What does this program print?

   print(f"{10 / 3:.2f}")

   Answer:

   3.33

   :.2f inside the braces shows the number with two decimal places.

7. [1 mark]What does this program print?

   word = "BugBot"
   print(word[0], word[3], word[-1])

   Answer:

   B B t

   Indexes count from 0, and -1 is the last character.

8. [1 mark]What does this program print?

   word = "BugBot"
   print(word[1:4])

   Answer:

   ugB

   A slice starts at the first index and stops before the second: indexes 1, 2 and 3.

9. [1 mark]What does this program print?

   message = "wall ahead"
   print(message.find("ahead"), message.find("ball"))

   Answer:

   5 -1

   find gives the index where the text starts, or -1 when it is not there.

10. [1 mark]OCR's name.substring(3, 3) on "BugBot" gives "Bot". What does the second 3 mean?

    1. ATake 3 characters
    2. BStop at index 3
    3. CStart at index 3
    4. DRepeat 3 times
    Answer: A. In the Exam Reference Language, substring takes a start index and a number of characters. Python's slice takes a stop index instead.

11. [1 mark]What is joining two strings together called?

    1. AConcatenation
    2. BSlicing
    3. CCasting
    4. DIteration
    Answer: A. Concatenation joins strings end to end, with + in Python.

The task: status report

# the two lines every program starts with: the commands, then the robot
from bugbot import *
connect()

forward(50, distance=10)
x, y = position()
print(f"BugBot at x={x} ...")

from bugbot import *
connect()
forward(50, distance=10)
x, y = position()
print(f'BugBot at x={x} y={y}, wall in {distance()} cm, battery {battery()}%')