def get_pattern(n=3, separator=' '):
a = 0
pattern = ''
for i in range(0, n):
for j in range(0, n):
pattern += str(a) + separator
a += 1
pattern = pattern.rstrip(separator) + '\n'
return pattern
# -- Call 1 --
pattern = get_pattern()
print(pattern)
# 0 1 2
# 3 4 5
# 6 7 8
# -- Call 2 --
pattern = get_pattern(separator='__')
print(pattern)
# 0__1__2
# 3__4__5
# 6__7__8
# -- Call 3 --
pattern = get_pattern(separator='__', n=5)
print(pattern)
# 0__1__2__3__4
# 5__6__7__8__9
# 10__11__12__13__14
# 15__16__17__18__19
# 20__21__22__23__24