Advanced FP Patterns — Series 3

Preview — 3 of 10 questions

What is the output of the following code?

javascript

from itertools import groupby, chain

data = [("a", 1), ("a", 2), ("b", 3), ("b", 4), ("a", 5)]
grouped = {k: [v for _, v in g] for k, g in groupby(data, key=lambda pair: pair[0])}
print(grouped)

flattened = list(chain.from_iterable(grouped.values()))
print(flattened)

A{'a': [5], 'b': [3, 4]}, [5, 3, 4]

B{'a': [1, 2, 5], 'b': [3, 4]}, [1, 2, 5, 3, 4]

C{'a': [1, 2], 'b': [3, 4]}, [1, 2, 3, 4]

D{'a': [5], 'b': [3, 4]}, [3, 4, 5]

What is the output of the following code?

javascript

import operator

words = ["  hello  ", "  world  "]
strip_call = operator.methodcaller("strip")
print(list(map(strip_call, words)))

replace_call = operator.methodcaller("replace", "o", "0")
print(list(map(replace_call, ["hello", "world"])))

A['hello', 'world'], ['hello', 'world']

B['hello', 'world'], ['hell0', 'w0rld']

C[' hello ', ' world '], ['hell0', 'w0rld']

D['hello', 'world'], TypeError: methodcaller() takes 1 positional argument but 3 were given

What is the output of the following code?

javascript

import functools

def memoize_by(key_func):
    def decorator(func):
        cache = {}
        @functools.wraps(func)
        def wrapper(*args):
            k = key_func(*args)
            if k not in cache:
                print(f"computing for key {k}")
                cache[k] = func(*args)
            return cache[k]
        return wrapper
    return decorator

@memoize_by(lambda a, b: (min(a, b), max(a, b)))
def combine(a, b):
    return f"{a}-{b}"

print(combine(1, 2))
print(combine(2, 1))
print(combine(3, 4))

Acomputing for key (1, 2), 1-2, 2-1, computing for key (3, 4), 3-4

Bcomputing for key (1, 2), 1-2, 1-2, 1-2

Ccomputing for key (1, 2), 1-2, 1-2, computing for key (3, 4), 3-4

Dcomputing for key (1, 2), 1-2, computing for key (2, 1), 2-1, computing for key (3, 4), 3-4

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