In Python, you are supposed to write a colon before you start a block, right?

So the rules can be rather simple:

• colon, with indentation = start of a new block

• colon, no indentation = an empty block (or a syntax error)

• no colon, with indentation = continuing of the previous line

• no colon, no indentation = next statement

• semicolon = statement boundary

Block ends where the indentation returns to the level of the line that opened the block. Continued line ends when indentation returns to the level of the starting line. (Where "to the level" = to the level, or below the level.)