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F1.3 Calling functions

Programming basics · GCSE · OCR J277 2.2.3, AQA 8525 3.2.10, Edexcel 1CP2 6.6.1 · about 15 min

What this lesson is about

Arguments, telling and asking, and notes on the robot's buzzer.

• A name, then brackets
• Arguments you can hear
• No brackets, nothing happens
• Some functions need nothing, some need several things
• Some arguments have names
• Telling versus asking
• The robot's functions so far

Questions 8 marks in all

1. [1 mark]In led("red"), what is "red" called?

   1. AAn argument
   2. BA function
   3. CA variable
   4. DA comment
   Answer: A. The information inside the brackets of a call is an argument. led is the function.

2. [1 mark]What happens when a program contains stop with no brackets?

   1. ANothing: the function is named but not called, and there is no error
   2. BThe robot stops
   3. CPython shows a SyntaxError
   4. DThe program ends
   Answer: A. The brackets are what call a function. Without them nothing happens, and Python does not complain: one of the quiet mistakes.

3. [1 mark]Which of these functions ask the robot something and give back an answer?

   Tick every answer that is true.

   1. Abattery()
   2. Bdistance()
   3. Cled("red")
   4. Dstop()
   Answer: A, B. battery and distance answer with a number. led and stop tell the robot to do something.

4. [1 mark]A program has the line battery() on its own. What does it show?

   1. ANothing: the answer comes back and is thrown away
   2. BThe battery percentage
   3. CAn error
   4. DThe word battery
   Answer: A. An asking function is only useful if you do something with its answer, such as print it: print(battery()).

5. [1 mark]In forward(50, distance=20), what is distance=20 called? (two words)

   Answer: named argument. An argument given as name=value is a named (or keyword) argument. The name says which piece of information it is.

6. [1 mark]led(255, 0, 0) makes the LED red. What does led(0, 0, 255) make it?

   1. ABlue
   2. BRed
   3. CGreen
   4. DOff
   Answer: A. The three arguments are red, green and blue, in that order, so the order of arguments matters.

7. [1 mark]tone(440, 0.5) plays a note. What does the 0.5 set?

   1. AHow long the note lasts, in seconds
   2. BHow high the note is
   3. CHow loud the note is
   4. DWhich robot plays it
   Answer: A. The first argument is the frequency in hertz, the second is the length in seconds. The order of the arguments matters.

8. [1 mark]battery() gives back a value and led("red") does not. In exam terms, which is a function and which is a procedure?

   1. Abattery() is a function, led("red") is a procedure
   2. Bbattery() is a procedure, led("red") is a function
   3. CBoth are procedures
   4. DBoth are variables
   Answer: A. A function returns a value; a procedure carries out a task and returns nothing. Python calls both functions.

The task: lights and numbers

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

led("...")
print("battery:", ...)

from bugbot import *
connect()
led('blue')
print('battery:', battery())
print('ahead:', distance())