N = 20 S = " " * N for i in range(N): S = S[1:] + "X" print(S)
Standard input is empty
X
XX
XXX
XXXX
XXXXX
XXXXXX
XXXXXXX
XXXXXXXX
XXXXXXXXX
XXXXXXXXXX
XXXXXXXXXXX
XXXXXXXXXXXX
XXXXXXXXXXXXX
XXXXXXXXXXXXXX
XXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXX