Intro

Notebook that explores with examples advanced Python topics like closures, decorators, generators, etc.

Decorator

"a callable that takes a function as an argument and returns a replacement function"



In [7]:

    
import functools



In [10]:

    
# decorator function, which does basic logging
def log(fun):
    @functools.wraps(fun)
    def wrapper(*args, **kw):
        print("Before decoration")
        result = fun(*args, **kw)
        print("After invocation")
        return result
    return wrapper



In [11]:

    
# base function
@log
def sum(a, b):
    return a + b

# equivalent to
#sum = log(sum)



In [12]:

    
sum(1,3)









    



Before decoration
After invocation






    Out[12]:





4

Mutable Default Argument Value

What will the following code print?



In [18]:

    
def test(n, l=[]):
    for i in range(n):
        l.append(i)
    print(l)



In [19]:

    
test(3)
test(3, [1,2,3])
test(3)









    



[0, 1, 2]
[1, 2, 3, 0, 1, 2]
[0, 1, 2, 0, 1, 2]



In [24]:

    
# it can be noticed that the mutable argument changes
# are memorized in the method signature
import inspect
inspect.signature(test)









    Out[24]:





<Signature (n, l=[0, 1, 2, 0, 1, 2])>



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