Week 7: Data Processing Patterns
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# Week 7: Data Processing Patterns > **Course:** Jan 2026 - Python > **Focus:** Recognizing filter/map/aggregate patterns in compact code. --- ## 1.
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Week 7: Data Processing Patterns
Course: Jan 2026 - Python Focus: Recognizing filter/map/aggregate patterns in compact code.
1. Core idea
Week 7 is about reading one expression and seeing the data pipeline hidden inside it.
What to remember
- Filtering keeps only some items.
- Mapping transforms each item.
- Aggregation combines many items into one output.
- Generator expressions often feed into
sum,join, ornext. - List comprehensions can combine filtering and mapping.
2. Common traps
- A single expression can contain more than one pattern.
sum(...)means aggregation, even if the inner part filters or maps.join(...)is aggregation over strings.next(...)means "take the first matching value."
3. Speedrun pattern
When you see a Week 7 question, ask:
- What gets removed?
- What gets transformed?
- What is the final collector doing?
4. Micro revision
- Filter = select
- Map = transform
- Aggregate = combine
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