def grow(a = []):
a.append(1)
return a
print(grow()) # [1]
print(grow()) # [1, 1]
print(grow()) # [1, 1, 1]
print(grow([2])) # [2, 1]
print(grow([2])) # [2, 1]
print(grow()) # [1, 1, 1, 1]
# [1, 1, 1, 1, 1] [1, 1, 1, 1, 1, 1]
print('\n', grow(), '\n', grow(), sep='') # wtf? [1, 1, 1, 1, 1, 1] [1, 1, 1, 1, 1, 1]
print(f'\n{grow()}\n{grow()}') # [1, 1, 1, 1, 1, 1, 1] [1, 1, 1, 1, 1, 1, 1, 1]