Menghilangkan loop

Menulis Kode Python yang Efisien

Logan Thomas

Scientific Software Technical Trainer, Enthought

Perulangan di Python

Pola perulangan:
- for loop: iterasi urutan satu per satu
- while loop: ulangi selama kondisi terpenuhi
- Loop "bersarang": satu loop di dalam loop lain
- Mahal!

Manfaat menghilangkan loop

Lebih sedikit baris kode
Keterbacaan lebih baik
- "Datar lebih baik daripada bersarang"
Lebih efisien

Hilangkan loop dengan built-in

# Daftar HP, Attack, Defense, Speed
poke_stats = [
    [90,  92, 75, 60],
    [25,  20, 15, 90],
    [65, 130, 60, 75],
    ...
]

alt=”Pokemon bernama Abomasnow, Abra, dan Absol beserta metadata Health Points, Attack, Defense, dan Speed yang disorot”

# Daftar HP, Attack, Defense, Speed
poke_stats = [
    [90,  92, 75, 60],
    [25,  20, 15, 90],
    [65, 130, 60, 75],
    ...
]

# Pendekatan for
totals = []
for row in poke_stats:
    totals.append(sum(row))

# List comprehension
totals_comp = [sum(row) for row in poke_stats]

# Fungsi bawaan map()
totals_map = [*map(sum, poke_stats)]

%%timeit
totals = []
for row in poke_stats:
    totals.append(sum(row))

140 µs ± 1.94 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)

%timeit totals_comp = [sum(row) for row in poke_stats]

114 µs ± 3.55 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)

%timeit totals_map = [*map(sum, poke_stats)]

95 µs ± 2.94 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)

Hilangkan loop dengan modul bawaan

poke_types = ['Bug', 'Fire', 'Ghost', 'Grass', 'Water']

# Pendekatan for bersarang
combos = []
for x in poke_types:
    for y in poke_types:
        if x == y:
            continue
        if ((x,y) not in combos) & ((y,x) not in combos):
            combos.append((x,y))

# Pendekatan modul bawaan
from itertools import combinations
combos2 = [*combinations(poke_types, 2)]

Hilangkan loop dengan NumPy

# Array HP, Attack, Defense, Speed
import numpy as np

poke_stats = np.array([
    [90,  92, 75, 60],
    [25,  20, 15, 90],
    [65, 130, 60, 75],
    ...
])

Hilangkan loop dengan NumPy

avgs = []
for row in poke_stats:
    avg = np.mean(row)
    avgs.append(avg)

print(avgs)

[79.25, 37.5, 82.5, ...]

avgs_np = poke_stats.mean(axis=1)

print(avgs_np)

[ 79.25  37.5   82.5  ...]

Hilangkan loop dengan NumPy

%timeit avgs = poke_stats.mean(axis=1)

23.1 µs ± 235 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)

%%timeit
avgs = []
for row in poke_stats:
    avg = np.mean(row)
    avgs.append(avg)

5.54 ms ± 224 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)

Ayo berlatih!

Menulis Kode Python yang Efisien