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Variables, Conditionals and Loops: Synthesis

≈ 30 min
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Synthesis

Link this topic to earlier and later ideas, then explain which relationship is transferable.

This extension applies that lens specifically to Variables, Conditionals and Loops.

From blocks to typed code

In block coding you drag instructions. In text programming you type them. Python is one of the most popular text languages, and the rules are strict but simple.

A variable is a labelled box that holds a value. You put a value in with = (the assignment sign):

name = "Thandi"
age = 14
litres = 25.5

Here name holds text (a string), age holds a whole number (an int), and litres holds a decimal (a float). You can read a box, change it, or use it in a calculation.

python

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Conditionals: making decisions

A program often has to choose. The if / elif / else structure lets it pick a path. Note the colon : and the indentation (4 spaces) that mark which lines belong inside each branch:

stage = 4
if stage == 0:
    print("No load-shedding")
elif stage <= 4:
    print("Moderate load-shedding")
else:
    print("Severe load-shedding")

Comparisons give a True/False answer: == (equal to), != (not equal), <, >, <=, >=.

Loops: repeating work

A loop repeats instructions so you do not copy-paste. A for loop repeats a set number of times; a while loop repeats as long as a condition stays True.

for day in range(1, 6):      # 1, 2, 3, 4, 5
    print("Study session", day)

charge = 20
while charge < 100:          # keep going until full
    charge = charge + 20

range(1, 6) counts 1 up to but not including 6.

python

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Coding: Text Programming Foundations — Synthesis: A learner runs this code:

units = 50
units = units - 18
units = units + 5
print(units)

What number is printed?

Coding: Text Programming Foundations — Synthesis: A loop adds up the numbers from 1 to 10:

total = 0
for n in range(1, 11):
    total = total + n
print(total)

What value does it print? (Remember range(1, 11) gives 1, 2, 3, ... up to 10.)

Coding: Text Programming Foundations — Synthesis: In an if statement, which Python keyword lets you test a second condition only when the first if was False? (One word.)

Name the original topic being extended by this synthesis lesson.

Which statement is the best evidence-led starting point for Variables, Conditionals and Loops: Synthesis?