Puzzle 16 Call Me Maybe

Python Brain Teasers — by Miki Tebeka (25 / 40)

👈 Where’s Waldo? | TOC | Endgame 👉

metrics.py

​ ​from​ ​functools​ ​import​ wraps
​ 
​ 
​ ​def​ ​metrics​(fn):
​     ncalls = 0
​     name = fn.__name__
​ 
​     @wraps(fn)
​     ​def​ ​wrapper​(*args, **kw):
​         ncalls += 1
​         ​print​(f​'{name} called {ncalls} times'​)
​ 
​     ​return​ wrapper
​ 
​ 
​ @metrics
​ ​def​ ​inc​(n):
​     ​return​ n + 1
​ 
​ 
​ inc(3)

Guess the Output

IMPORTANT

Try to guess what the output is before moving to the next page.

This code will raise an UnboundLocalError exception.

When you have a variable (name) in Python (say, cart = [’lamp’]), you can do two operations:

Mutate
Change the object the variable is pointing to (e.g., cart.append(’mug’))

Rebind
Have the variable point to another object (e.g., cart = [’carrots’])