Python Brain Teasers/

...

/

Puzzle 16: Explanation

Puzzle 16: Explanation

Let’s look at the scope of variables in Python and the cause of the `UnboundLocalError` exception.

We'll cover the following...

Try it yourself

Try executing the code below to verify the result:

Press + to interact
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)

Explanation

When we have a variable, or name, in Python like cart = [‘lamp’]), we can do two operations:

  • Mutate the variable by changing the object that the variable is pointing to ( cart.append(‘mug’)).
...
Access this course and 1400+ top-rated courses and projects.