какие знания должны быть чтобы быть на уровне джуна.
a = []
for i in range(3):
a.append([])
# --- --- ---
a = [[] for _ in range(3)]
k = 1
a = []
for i in range(3):
...
k = k + 1
# --- --- ---
a = [[i, i+1, i+2] for i in range(1, 8, 3)]
for i in range(3):
print(*a[i])
# --- --- ---
for i in a:
print(*i)
from more_itertools import chunked
a = list(chunked(range(1, 10), 3))