Python syntax: quotes, colons and indentation

The idea

You can read a sentence with missing punctuation, but a programming language needs a dependable way to separate its parts. Treat each symbol as a signpost. Quotes mark text; parentheses supply information to a function call; a colon introduces a block after statements such as if and for. Indentation tells Python which instructions belong to that block. Use four spaces consistently in these examples.

A tiny experiment

has_key = True
if has_key:
    print("The door opens.")
print("Keep exploring.")

The door opens.
Keep exploring.

Read it one step at a time

1. True is a Boolean value, so it is not in quotes. # can introduce a comment for a human reader.
2. The colon ends the if header. The indented print belongs to that decision.
3. The final print is back at the left edge. It runs whether or not the key is present.

Make one change

Change True to False. Predict both output lines before running.

Keep following the trail

• Activity 01: Your first message
• Activity 05: Which note matches?
• Activity 11: Build your own choice

Sources & further reading

• Python’s design FAQ

Companion notes for Coding Adventure by James Colby. Historical claims link to their sources; the examples are written for this learning trail.