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Lesson 2: Peter’s Treasure List

Why?

A list holds many things. We can add and pick items by number spots.

What to type

  • Make chest = ["ruby", "diamond"]
  • Add: chest.append("sapphire")
  • Print first & last: print(chest[0], chest[-1])
⭐ Stars: 0
🐞 Bugs: 0

Go to Practice → 



    

      Hint
      
Square brackets [ ] are a treasure chest. chest[0] is the first item; chest[-1] is the last.

    

  





from js import document, localStorage, window
import sys, io

START = '''# A treasure chest is a list (like a row of boxes)
chest = ["ruby", "diamond"]
# add a new gem
chest.append("sapphire")
# print first and last
print(chest[0], chest[-1])  # should show: ruby sapphire
'''
SOLN = '''chest = ["ruby", "diamond"]
chest.append("sapphire")
print(chest[0], chest[-1])
'''

def gi(k):
    v = localStorage.getItem(k)
    try: return int(v) if v is not None else 0
    except: return 0
def setb(stars=None, bugs=None):
    if stars is not None: localStorage.setItem('stars', str(stars))
    if bugs  is not None: localStorage.setItem('bugs',  str(bugs))
    document.getElementById('stars').textContent = f'⭐ Stars: {gi("stars")}'
    document.getElementById('bugs').textContent  = f'🐞 Bugs: {gi("bugs")}'

def run(evt):
    src = document.getElementById('editor').value
    out_el = document.getElementById('out')
    ns = {}
    f = io.StringIO()
    try:
        old = sys.stdout; sys.stdout = f
        try: exec(src, ns)
        finally: sys.stdout = old
        output = f.getvalue()
        assert 'chest' in ns and isinstance(ns['chest'], list), "Make a list named chest."
        assert ns['chest'][0] == "ruby", "First item should be 'ruby'."
        assert ns['chest'][-1] == "sapphire", "Last item should be 'sapphire'."
        out_el.textContent = (output or "") + "All checks passed! ⭐"
        setb(stars=gi('stars')+1)
        try: window.confetti()
        except: pass
    except Exception as e:
        out_el.textContent = "Bug found: " + str(e)
        setb(bugs=gi('bugs')+1)

document.getElementById('run').addEventListener('click', run)
document.getElementById('fill-start').addEventListener('click',
  lambda e: setattr(document.getElementById('editor'), 'value', START))
document.getElementById('fill-solution').addEventListener('click',
  lambda e: setattr(document.getElementById('editor'), 'value', SOLN))
if not document.getElementById('editor').value:
  document.getElementById('editor').value = START
setb()