← Back Peter

Lesson 1: add(a, b)

Why?

A function is a named trick Peter can do. This one adds two numbers and gives them back.

What to type

  • Write def add(a, b):
  • Return the sum with return a + b
  • Test it: print(add(2, 3))
⭐ Stars: 0
🐞 Bugs: 0

Next Lesson → 



    

      Hint
      
def starts a function. return hands back the answer.

    

  





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

START = '''# Make add(a, b), then print the answer
def add(a, b):
    # return the sum
    pass

print(add(2, 3))  # should show 5
'''
SOLN = '''def add(a, b):
    return a + b

print(add(2, 3))
'''

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 'add' in ns, "Define a function named add(a, b)."
        assert ns['add'](2,3) == 5, "add(2,3) should be 5."
        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()