Python Programming For Beginners

• Statement - a single line instruction Python can execute (e.g., print(...), x = 3 ).

Active Recall

• Syntax: __________________________________________________

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• Indentation: __________________________________________________

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• Block: __________________________________________________

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• Parse time: __________________________________________________

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• SyntaxError: __________________________________________________

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• IndentationError: __________________________________________________

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• Statement: __________________________________________________

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Worked Examples

Example 1: Basic print and assignment

• Write a valid statement: name = "Ada"

• Output it with a correct syntax call: print(name)

• Python runs in order: assignment first, then printing.

Now you try:

Write two lines to assign x = 5 and print x.

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Example 2: If-statement indentation

• Use a header with a colon: if x > 0:

• Indent the statements that belong to the block (same indentation level).

• Do not indent lines that should run outside the block.

Now you try:

Write code that prints "positive" only when n > 0.

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Example 3: Detecting indentation mistakes

• Consider this pattern (wrong):

• Header ends with:

• Next line is not indented

• Python treats the block as missing → IndentationError (or similar).

• Fix by indenting the block consistently.

Now you try:

Identify the indentation rule: after if flag: the next line must be ____________________.

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Practice Questions

• (4-mark) Describe what Python uses indentation for, and why if condition: needs the following lines indented.

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• (4-mark) Give one example of a SyntaxError cause (e.g., missing bracket/quote) and state what happens when it occurs.

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• (8-mark) Explain the difference between SyntaxError and IndentationError, including when each is detected (parse time vs block formatting).

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• (8-mark) A student writes this:

• if score >= 50:

• print("Pass")

• print("Done")

Explain what will run and how indentation affects the output.

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• (Hard, 12-mark) “Most Python exam mistakes on this topic are caused by misunderstanding indentation rather than syntax.” How far do you agree? Use at least two examples in your answer (one about syntax, one about indentation), and explain the consequences.

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• (Medium, 8-mark) Write a short code snippet using if, else, and print that outputs "A" when v < 10, otherwise outputs "B".

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Answer Key

• Indentation groups lines into the block controlled by if...:; without it Python cannot tell what belongs to the block.

• Example: missing a closing quote in print("hi) causes SyntaxError; code fails to parse and does not run.

• SyntaxError: incorrect grammar (punctuation/quotes/brackets) detected at parse time. IndentationError: incorrect/missing indentation for a block, also detected while parsing/structuring blocks.

• print("Pass") runs only if score >= 50 and print("Done") always runs (because it is not indented into the if block).

• Example agreement: indentation mistakes commonly

lead to incorrect block grouping, while syntax mistakes stop the program from starting at all. For syntax, missing: after if (or an unmatched quote) prevents parsing. For indentation, using the wrong level can make a line run under the wrong condition (or not at all).

Exam Tips & Common Mistakes

• Mistake: Missing: after if, for, while, def → Python can’t parse the statement; you get a syntax-style error.

• Mistake: Wrong indentation level (e.g., 2 spaces vs 4) → Python may raise an indentation-related error or run the wrong lines.

• Mistake: Mixing tabs and spaces → Visual alignment can lie; Python treats them differently, causing block errors.

• Mistake: Using indentation where it doesn’t belong → Lines may become part of a block you didn’t intend (e.g., print inside/outside an if ).

• Mistake: Expecting Python to “guess” the block → Python never infers block structure from spacing patterns - indentation defines it.

Examiner-focused tips:

• For 8-mark questions, explain what the error is and what Python does next (parse-time failure vs block formatting issue).

• Use correct terms: SyntaxError (grammar) vs IndentationError (block formatting).

• When describing code output, mention exactly which lines are inside the indented block.

Quick Reference

Rules (exam-ready)

• Colon rule: if condition: must end with:.

• Block rule: every line controlled by that statement must be indented consistently.

• Consistent indentation: use spaces (commonly 4) and don’t mix tabs.

• Parse time vs runtime:

• Syntax/structure errors: detected before the program can run.

• Indentation/block mistakes: detected while Python structures the code.

Mnemonic

• C-B-I: C olon ends the header, B lock is indented, I ndentation must be consistent.

Absolute essentials

• A line ending with: starts a block.

• Indentation decides what belongs inside the block.

• Syntax errors stop execution; indentation errors break block structure.

• print(...) only runs when it is actually reached in the correct block.

Confidence Check

• I can explain what indentation means in Python blocks. [ ] 1 [ ] 2 [ ] 3 [ ] 4 [ ] 5

• I can predict output from an if statement with correct indentation. [ ] 1 [ ] 2 [ ] 3 [ ] 4 [ ] 5

• I can distinguish SyntaxError from IndentationError. [ ] 1

End of chapter one. 7 more chapters in the full book.