/Python & Data Analytics/Phase 2

Phase 2Days 13-24

Python Problem Solving & Program Design

Build reliable analytical utilities instead of notebook fragments

Phase Goal

Use collections, functions, modules, and tests to turn repeated analysis into understandable programs.

Progress

Notes

Open the written lectures for this course before checking off the phase topics.

Projects

Community Pantry Stock Reconciliation

Day 13: Tuples, Sets & Collection Choice

Build the first-principles mental model for Tuple packing, unpacking, and immutable returns; name the question it answers and the unit of analysisPredict and trace a tiny example of Tuple packing, unpacking, and immutable returns before inspecting the resultApply Tuple packing, unpacking, and immutable returns to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Tuple packing, unpacking, and immutable returns; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Set uniqueness, membership, and set algebra; name the question it answers and the unit of analysisPredict and trace a tiny example of Set uniqueness, membership, and set algebra before inspecting the resultApply Set uniqueness, membership, and set algebra to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Set uniqueness, membership, and set algebra; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for List versus tuple versus set decisions; name the question it answers and the unit of analysisPredict and trace a tiny example of List versus tuple versus set decisions before inspecting the resultApply List versus tuple versus set decisions to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind List versus tuple versus set decisions; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Hashability, order assumptions, and accidental deduplication; name the question it answers and the unit of analysisPredict and trace a tiny example of Hashability, order assumptions, and accidental deduplication before inspecting the resultApply Hashability, order assumptions, and accidental deduplication to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Hashability, order assumptions, and accidental deduplication; diagnose the visible failure and perform the corrective check

Retrieve one recent mechanism and one older prerequisite before consulting notesComplete a guided example, then reconstruct its critical path from a blank artifactSolve a changed task that requires choosing among already-taught toolsRecord the decision changed, failure tested, help used, and adaptive 1/3/7/14/30-day review cue

Day 14: Comprehensions Without Hidden Logic

Build the first-principles mental model for List comprehensions; name the question it answers and the unit of analysisPredict and trace a tiny example of List comprehensions before inspecting the resultApply List comprehensions to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind List comprehensions; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Set and dictionary comprehensions; name the question it answers and the unit of analysisPredict and trace a tiny example of Set and dictionary comprehensions before inspecting the resultApply Set and dictionary comprehensions to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Set and dictionary comprehensions; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Filtering versus transforming; name the question it answers and the unit of analysisPredict and trace a tiny example of Filtering versus transforming before inspecting the resultApply Filtering versus transforming to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Filtering versus transforming; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Loop expansion and nested-comprehension limits; name the question it answers and the unit of analysisPredict and trace a tiny example of Loop expansion and nested-comprehension limits before inspecting the resultApply Loop expansion and nested-comprehension limits to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Loop expansion and nested-comprehension limits; diagnose the visible failure and perform the corrective check

Day 15: Function Contracts & Validation

Build the first-principles mental model for Preconditions, postconditions, and invariants; name the question it answers and the unit of analysisPredict and trace a tiny example of Preconditions, postconditions, and invariants before inspecting the resultApply Preconditions, postconditions, and invariants to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Preconditions, postconditions, and invariants; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Guard clauses and validation messages; name the question it answers and the unit of analysisPredict and trace a tiny example of Guard clauses and validation messages before inspecting the resultApply Guard clauses and validation messages to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Guard clauses and validation messages; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Positional, keyword, default, *args, and **kwargs; name the question it answers and the unit of analysisPredict and trace a tiny example of Positional, keyword, default, *args, and **kwargs before inspecting the resultApply Positional, keyword, default, *args, and **kwargs to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Positional, keyword, default, *args, and **kwargs; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Mutable defaults, coercion, and oversized functions; name the question it answers and the unit of analysisPredict and trace a tiny example of Mutable defaults, coercion, and oversized functions before inspecting the resultApply Mutable defaults, coercion, and oversized functions to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Mutable defaults, coercion, and oversized functions; diagnose the visible failure and perform the corrective check

Day 16: Scope, Closures & Functional Tools

Build the first-principles mental model for LEGB name lookup; name the question it answers and the unit of analysisPredict and trace a tiny example of LEGB name lookup before inspecting the resultApply LEGB name lookup to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind LEGB name lookup; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Closures as remembered configuration; name the question it answers and the unit of analysisPredict and trace a tiny example of Closures as remembered configuration before inspecting the resultApply Closures as remembered configuration to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Closures as remembered configuration; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for lambda boundaries; name the question it answers and the unit of analysisPredict and trace a tiny example of lambda boundaries before inspecting the resultApply lambda boundaries to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind lambda boundaries; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for map/filter versus comprehensions; name the question it answers and the unit of analysisPredict and trace a tiny example of map/filter versus comprehensions before inspecting the resultApply map/filter versus comprehensions to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind map/filter versus comprehensions; diagnose the visible failure and perform the corrective check

Day 17: Modules, Imports & Packages

Build the first-principles mental model for Module namespaces and import styles; name the question it answers and the unit of analysisPredict and trace a tiny example of Module namespaces and import styles before inspecting the resultApply Module namespaces and import styles to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Module namespaces and import styles; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for __name__ and script-versus-import behavior; name the question it answers and the unit of analysisPredict and trace a tiny example of __name__ and script-versus-import behavior before inspecting the resultApply __name__ and script-versus-import behavior to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind __name__ and script-versus-import behavior; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Package folders and dependency direction; name the question it answers and the unit of analysisPredict and trace a tiny example of Package folders and dependency direction before inspecting the resultApply Package folders and dependency direction to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Package folders and dependency direction; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Circular imports and shadowed names; name the question it answers and the unit of analysisPredict and trace a tiny example of Circular imports and shadowed names before inspecting the resultApply Circular imports and shadowed names to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Circular imports and shadowed names; diagnose the visible failure and perform the corrective check

Day 18: Testing Small Data Functions

Build the first-principles mental model for Example tests and edge cases; name the question it answers and the unit of analysisPredict and trace a tiny example of Example tests and edge cases before inspecting the resultApply Example tests and edge cases to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Example tests and edge cases; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for pytest arrange-act-assert; name the question it answers and the unit of analysisPredict and trace a tiny example of pytest arrange-act-assert before inspecting the resultApply pytest arrange-act-assert to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind pytest arrange-act-assert; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Parameterized boundary tests; name the question it answers and the unit of analysisPredict and trace a tiny example of Parameterized boundary tests before inspecting the resultApply Parameterized boundary tests to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Parameterized boundary tests; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Happy-path-only false confidence; name the question it answers and the unit of analysisPredict and trace a tiny example of Happy-path-only false confidence before inspecting the resultApply Happy-path-only false confidence to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Happy-path-only false confidence; diagnose the visible failure and perform the corrective check

Day 19: Iterators, Generators & Large Inputs

Build the first-principles mental model for Iterable versus iterator; name the question it answers and the unit of analysisPredict and trace a tiny example of Iterable versus iterator before inspecting the resultApply Iterable versus iterator to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Iterable versus iterator; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for yield and lazy evaluation; name the question it answers and the unit of analysisPredict and trace a tiny example of yield and lazy evaluation before inspecting the resultApply yield and lazy evaluation to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind yield and lazy evaluation; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Streaming rows rather than loading all records; name the question it answers and the unit of analysisPredict and trace a tiny example of Streaming rows rather than loading all records before inspecting the resultApply Streaming rows rather than loading all records to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Streaming rows rather than loading all records; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Exhaustion, one-pass bugs, and memory checks; name the question it answers and the unit of analysisPredict and trace a tiny example of Exhaustion, one-pass bugs, and memory checks before inspecting the resultApply Exhaustion, one-pass bugs, and memory checks to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Exhaustion, one-pass bugs, and memory checks; diagnose the visible failure and perform the corrective check

Day 20: Sorting, Keys & Ranking Rules

Build the first-principles mental model for sorted versus list.sort; name the question it answers and the unit of analysisPredict and trace a tiny example of sorted versus list.sort before inspecting the resultApply sorted versus list.sort to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind sorted versus list.sort; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Key functions and multi-field order; name the question it answers and the unit of analysisPredict and trace a tiny example of Key functions and multi-field order before inspecting the resultApply Key functions and multi-field order to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Key functions and multi-field order; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Stable sorting and deterministic ties; name the question it answers and the unit of analysisPredict and trace a tiny example of Stable sorting and deterministic ties before inspecting the resultApply Stable sorting and deterministic ties to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Stable sorting and deterministic ties; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Missing values and unjustified top-N rules; name the question it answers and the unit of analysisPredict and trace a tiny example of Missing values and unjustified top-N rules before inspecting the resultApply Missing values and unjustified top-N rules to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Missing values and unjustified top-N rules; diagnose the visible failure and perform the corrective check

Day 21: Dates, Times & Reporting Periods

Build the first-principles mental model for date, datetime, timedelta, parsing, and formatting; name the question it answers and the unit of analysisPredict and trace a tiny example of date, datetime, timedelta, parsing, and formatting before inspecting the resultApply date, datetime, timedelta, parsing, and formatting to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind date, datetime, timedelta, parsing, and formatting; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Calendar periods versus rolling windows; name the question it answers and the unit of analysisPredict and trace a tiny example of Calendar periods versus rolling windows before inspecting the resultApply Calendar periods versus rolling windows to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Calendar periods versus rolling windows; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Time zones and local dates; name the question it answers and the unit of analysisPredict and trace a tiny example of Time zones and local dates before inspecting the resultApply Time zones and local dates to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Time zones and local dates; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Inclusive endpoints and period boundaries; name the question it answers and the unit of analysisPredict and trace a tiny example of Inclusive endpoints and period boundaries before inspecting the resultApply Inclusive endpoints and period boundaries to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Inclusive endpoints and period boundaries; diagnose the visible failure and perform the corrective check

Day 22: Decimal, Money & Rounding

Build the first-principles mental model for Binary floating-point failure; name the question it answers and the unit of analysisPredict and trace a tiny example of Binary floating-point failure before inspecting the resultApply Binary floating-point failure to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Binary floating-point failure; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Decimal construction and quantization; name the question it answers and the unit of analysisPredict and trace a tiny example of Decimal construction and quantization before inspecting the resultApply Decimal construction and quantization to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Decimal construction and quantization; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Currency units and percentage points; name the question it answers and the unit of analysisPredict and trace a tiny example of Currency units and percentage points before inspecting the resultApply Currency units and percentage points to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Currency units and percentage points; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Premature rounding and reconciliation gaps; name the question it answers and the unit of analysisPredict and trace a tiny example of Premature rounding and reconciliation gaps before inspecting the resultApply Premature rounding and reconciliation gaps to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Premature rounding and reconciliation gaps; diagnose the visible failure and perform the corrective check

Day 23: Command-Line Analytical Utilities

Build the first-principles mental model for argparse contracts; name the question it answers and the unit of analysisPredict and trace a tiny example of argparse contracts before inspecting the resultApply argparse contracts to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind argparse contracts; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Input/output paths and dry runs; name the question it answers and the unit of analysisPredict and trace a tiny example of Input/output paths and dry runs before inspecting the resultApply Input/output paths and dry runs to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Input/output paths and dry runs; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Logging versus result output; name the question it answers and the unit of analysisPredict and trace a tiny example of Logging versus result output before inspecting the resultApply Logging versus result output to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Logging versus result output; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Idempotent reruns and overwrite protection; name the question it answers and the unit of analysisPredict and trace a tiny example of Idempotent reruns and overwrite protection before inspecting the resultApply Idempotent reruns and overwrite protection to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Idempotent reruns and overwrite protection; diagnose the visible failure and perform the corrective check

Day 24: Phase Project — Pantry Reconciliation

Build the first-principles mental model for Record contracts and unit definitions; name the question it answers and the unit of analysisPredict and trace a tiny example of Record contracts and unit definitions before inspecting the resultApply Record contracts and unit definitions to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Record contracts and unit definitions; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Reusable parsing, validation, matching, and ranking; name the question it answers and the unit of analysisPredict and trace a tiny example of Reusable parsing, validation, matching, and ranking before inspecting the resultApply Reusable parsing, validation, matching, and ranking to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Reusable parsing, validation, matching, and ranking; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Tests for duplicates, missing IDs, and unit mismatch; name the question it answers and the unit of analysisPredict and trace a tiny example of Tests for duplicates, missing IDs, and unit mismatch before inspecting the resultApply Tests for duplicates, missing IDs, and unit mismatch to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Tests for duplicates, missing IDs, and unit mismatch; diagnose the visible failure and perform the corrective check

Build the first-principles mental model for Operator report, transfer scenario, and runbook; name the question it answers and the unit of analysisPredict and trace a tiny example of Operator report, transfer scenario, and runbook before inspecting the resultApply Operator report, transfer scenario, and runbook to a realistic analyst decision while stating assumptions, units, and boundariesBreak one assumption behind Operator report, transfer scenario, and runbook; diagnose the visible failure and perform the corrective check

Deliver Community Pantry Stock Reconciliation for a volunteer pantry operations lead; support the decision: which staples require redistribution before the weekend?Reconstruct the critical workflow without the example open and disclose help usedFind and repair a planted data, logic, or communication failure with evidenceRespond to a changed requirement without being told which technique to useState limitations, non-goals, uncertainty, and what evidence would change the recommendation

Capstone

Community Pantry Stock Reconciliation

Build for a volunteer pantry operations lead. The result must support this decision: which staples require redistribution before the weekend? Include reproducible inputs, validation evidence, one tested failure, a changed requirement, and an explicit non-goal.

Reproducible source-to-output workflow
Documented quality checks and assumptions
Decision-ready output for a named user
Independent reconstruction and transfer evidence

Phase Complete!

After this phase, you'll be able to:

Tuples, Sets & Collection Choice
Comprehensions Without Hidden Logic
Function Contracts & Validation
Scope, Closures & Functional Tools
Modules, Imports & Packages
Testing Small Data Functions
Iterators, Generators & Large Inputs
Sorting, Keys & Ranking Rules

Independently deliver Community Pantry Stock Reconciliation, diagnose a planted failure, explain the decision logic, and transfer the workflow to a changed requirement.

Back to all phases

Phase Goal

Day 13: Tuples, Sets & Collection Choice

Tuple packing, unpacking, and immutable returns

Set uniqueness, membership, and set algebra

List versus tuple versus set decisions

Hashability, order assumptions, and accidental deduplication

Practice, retrieval, and analyst judgment

Day 14: Comprehensions Without Hidden Logic

List comprehensions

Set and dictionary comprehensions

Filtering versus transforming

Loop expansion and nested-comprehension limits

Practice, retrieval, and analyst judgment

Day 15: Function Contracts & Validation

Preconditions, postconditions, and invariants

Guard clauses and validation messages

Positional, keyword, default, *args, and **kwargs

Mutable defaults, coercion, and oversized functions

Practice, retrieval, and analyst judgment

Day 16: Scope, Closures & Functional Tools

LEGB name lookup

Closures as remembered configuration

lambda boundaries

map/filter versus comprehensions

Practice, retrieval, and analyst judgment

Day 17: Modules, Imports & Packages

Module namespaces and import styles

__name__ and script-versus-import behavior

Package folders and dependency direction

Circular imports and shadowed names

Practice, retrieval, and analyst judgment

Day 18: Testing Small Data Functions

Example tests and edge cases

pytest arrange-act-assert

Parameterized boundary tests

Happy-path-only false confidence

Practice, retrieval, and analyst judgment

Day 19: Iterators, Generators & Large Inputs

Iterable versus iterator

yield and lazy evaluation

Streaming rows rather than loading all records

Exhaustion, one-pass bugs, and memory checks

Practice, retrieval, and analyst judgment

Day 20: Sorting, Keys & Ranking Rules

sorted versus list.sort

Key functions and multi-field order

Stable sorting and deterministic ties

Missing values and unjustified top-N rules

Practice, retrieval, and analyst judgment

Day 21: Dates, Times & Reporting Periods

date, datetime, timedelta, parsing, and formatting

Calendar periods versus rolling windows

Time zones and local dates

Inclusive endpoints and period boundaries

Practice, retrieval, and analyst judgment

Day 22: Decimal, Money & Rounding

Binary floating-point failure

Decimal construction and quantization

Currency units and percentage points

Premature rounding and reconciliation gaps

Practice, retrieval, and analyst judgment

Day 23: Command-Line Analytical Utilities

argparse contracts

Input/output paths and dry runs

Logging versus result output

Idempotent reruns and overwrite protection

Practice, retrieval, and analyst judgment

Day 24: Phase Project — Pantry Reconciliation

Record contracts and unit definitions

Reusable parsing, validation, matching, and ranking

Tests for duplicates, missing IDs, and unit mismatch

Operator report, transfer scenario, and runbook

Phase gate: independent delivery and transfer

Community Pantry Stock Reconciliation

Phase Complete!

name and script-versus-import behavior