Someone else had some code in some other language that was something like the following couple of cells.



In [1]:

    
roman_letter_values = (
    ('I', 1),
    ('V', 5),
    ('X', 10),
    ('L', 50),
    ('C', 100),
    ('D', 500),
    ('M', 1000),
)



In [2]:

    
for i, (letter, value) in enumerate(roman_letter_values):
    if i % 2 == 1:
        print(i, letter, value)

I know what the code above means, but I have to think about it. It was hard to understand, because the test above as repeated below, is so indirect.

if i % 2 == 1:

Compare that with the directness of the following test from cell #12.

if significant_digits(value) == 5:



In [3]:

    
def prime_factors(x):
    divisor = 2
    while divisor < x:
        if x % divisor == 0:
            yield divisor
            x //= divisor
            continue
        divisor += 1
    yield x



In [4]:

    
for letter, value in roman_letter_values:
    print(letter, value, list(prime_factors(value)))









    



I 1 [1]
V 5 [5]
X 10 [2, 5]
L 50 [2, 5, 5]
C 100 [2, 2, 5, 5]
D 500 [2, 2, 5, 5, 5]
M 1000 [2, 2, 2, 5, 5, 5]



In [5]:

    
def significant_digits(x):
    return int(''.join(reversed(str(x))))



In [6]:

    
def foo():
    for letter, value in roman_letter_values:
        print(letter, value, significant_digits(value))



In [7]:

    
foo()



In [8]:

    
def significant_digits(x):
    return int(str(x).rstrip('0'))



In [9]:

    
foo()



In [10]:

    
def significant_digits(x):
    while x % 10 == 0:
        x //= 10
    return x



In [11]:

    
foo()



In [12]:

    
for letter, value in roman_letter_values:
    if significant_digits(value) == 5:
        print(letter, value)

Of the three different implementations of significant_digits() above, which do you like the most? Which do you dislike the most? How would you write significant_digits()?