What is the purpose of the colon before a block in Python?

Question

What is the purpose of the colon before a block in Python?

Example:

if n == 0:
    print \"The end\"

Answer 1

Consider the following list of things to buy from the grocery store, written in Pewprikanese.

pewkah
lalala
    chunkykachoo
    pewpewpew
skunkybacon

When I read that, I'm confused, Are chunkykachoo and pewpewpew a kind of lalala? Or what if chunkykachoo and pewpewpew are indented just because they are special items?

Now see what happens when my Pewprikanese friend add a colon to help me parse the list better: (<-- like this)

pewkah
lalala:   (<-- see this colon)
    chunkykachoo
    pewpewpew
skunkybacon

Now it's clear that chunkykachoo and pewpewpew are a kind of lalala.

Let's say there is a person who's starting to learn Python, which happens to be her first programming language to learn. Without colons, there's a considerable probability that she's going to keep thinking "this lines are indented because this lines are like special items.", and it could take a while to realize that that's not the best way to think about indentation.