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feat(examples): add Streamlit cleaning app recipe - #517

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JohnnyWilson16 merged 3 commits into
FreshCode-Org:mainfrom
satheesh142002:feat/511-streamlit-app
Oct 6, 2026
Merged

JohnnyWilson16 merged 3 commits into
FreshCode-Org:mainfrom
satheesh142002:feat/511-streamlit-app

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@satheesh142002

@satheesh142002 satheesh142002 commented Oct 4, 2026 •

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What changed?

Added streamlit_app.py, a standalone Streamlit app with CSV upload, fallback demo data, before/after previews, cleaning metrics, a quality report, and cleaned CSV download. Registered it in README.md.

Why?

Provides an interactive way to explore FreshData cleaning. Fixes #511.

How was it tested?

  • New unit tests added in tests (not applicable; this adds an example recipe)
  • Ran fast CI lane locally: pytest -m "not online and not large"
  • Ran linting: uvx ruff check examples/integrations/streamlit_app.py
  • Ran type checks: mypy src/freshdata

Also verified Python syntax with python -m py_compile and checked the diff with git diff --check.

Any performance impact?

  • None / negligible

Any compatibility concerns?

  • None / fully backward-compatible

Documentation updated?

  • Documentation updated in docs
  • Examples updated
  • Note added under [Unreleased] in CHANGELOG.md

Summary by CodeRabbit

  • New Features
    • Added an interactive CSV-cleaning app that works with sample data or uploaded CSV files. It displays raw and cleaned data previews, along with cleaning metrics, a quality report, and available cleaning actions.
    • Users can download the cleaned data as a CSV. The app also reports errors when an uploaded CSV cannot be read or data cleaning fails.
    • Added the Streamlit app to the examples integration guide.

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📝 Walkthrough

Walkthrough

Adds a Streamlit app that loads sample data or an uploaded CSV, cleans it with FreshData, and displays cleaning metrics, data previews, a download, and a quality report. The examples index links to the app.

Changes

Streamlit Data-Cleaning App

Layer / File(s) Summary
Load data and run cleaning
examples/README.md, examples/integrations/streamlit_app.py
The app uses sample data or parses an uploaded CSV. It displays an error and stops if CSV parsing or cleaning fails. It calls fd.clean with report generation. The examples index links to the app.
Display cleaning results
examples/integrations/streamlit_app.py
The app shows cleaning metrics, raw and cleaned DataFrames, a cleaned CSV download, and an expandable quality report with action details.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~15 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  actor User
  participant StreamlitApp as streamlit_app.py
  participant FreshData
  User->>StreamlitApp: Upload CSV or use sample data
  StreamlitApp->>StreamlitApp: Parse uploaded CSV
  StreamlitApp->>FreshData: fd.clean(data, return_report=True)
  FreshData-->>StreamlitApp: Cleaned data and report
  StreamlitApp-->>User: Show metrics, previews, download, and report
Loading

Suggested reviewers: johnnywilson-portfolio

Merge Risk: ⚪ Minimal · up to 84017

The app provides the documented cleaning previews, metrics, report, and CSV download. No issue identified here needs resolution before merge.

🚥 Pre-merge checks | ✅ 5
✅ Passed checks (5 passed)
Check name Status Explanation
Title check ✅ Passed The title clearly summarizes the main change: adding a Streamlit cleaning app recipe.
Description check ✅ Passed The description covers what changed, why, testing, performance, compatibility, and documentation. It identifies issue #511 and lists the checks that were run; the unchecked CI and type-check items are…
Linked Issues check ✅ Passed Issue #511 is implemented in examples/integrations/streamlit_app.py. The app accepts CSV uploads, uses demo data when no file is uploaded, calls fd.clean(..., return_report=True), displays raw and…
Out of Scope Changes check ✅ Passed The reviewed changes add the Streamlit recipe, adjust its missing-value metric, and register the recipe in examples/README.md. These changes support issue #511. No unrelated change is identified in …
Docstring Coverage ✅ Passed Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 1 files.
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Actionable comments posted: 1


  • 🪄 Fix CodeRabbit comments on this PR
🤖 Prompt to fix review comments
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only still-valid issues, skip the rest with a brief reason, keep changes
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Inline comments:
Review comments at @examples/integrations/streamlit_app.py:
- Line 76: Update the imputed-value count in the report action aggregation to
include automatic actions with `step == "missing"` as well as `"impute"`, and
count only fill actions by checking that `action.description` starts with
“filled ”; retain the positive-count filter.

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Comment thread examples/integrations/streamlit_app.py Outdated
@satheesh142002

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Thanks for contributing the Streamlit integration recipe, @satheesh142002! The recipe provides a clean, practical demo of interactive CSV cleaning with FreshData, side-by-side previews, metric cards, and a download button.

Before we can merge, please address the following issues:

1. Inaccurate "Columns Modified" Metric (Skipped Actions Counted)

Location: examples/integrations/streamlit_app.py:38-46

def count_modified_columns(report: object) -> int:
    modified = set(report.columns_imputed)
    modified.update(
        action.column
        for action in report.actions
        if action.column is not None and action.count > 0
    )
    return len(modified)

Issue: When FreshData protects identifier columns or sensitive columns from modification (e.g. semantic identifier protection), it records an action with count > 0 and status="skipped". Because count_modified_columns only checks action.count > 0, columns that were intentionally protected and left unchanged are counted as "modified". Additionally, completely dropped columns (report.columns_dropped) are missed because table-level drop actions have action.column is None.
Fix:

def count_modified_columns(report: Any) -> int:
    """Count columns modified by applied cleaning actions, imputations, or drops."""
    modified = set(report.columns_imputed) | set(report.columns_dropped)
    modified.update(
        action.column
        for action in report.actions
        if action.column is not None
        and action.count > 0
        and getattr(action, "status", "automatic") in {"automatic", "approved"}
    )
    return len(modified)

2. Fragile String Matching for Imputed Values

Location: examples/integrations/streamlit_app.py:75-81

imputed_values = sum(
    action.count
    for action in report.actions
    if action.step in {"impute", "missing"}
    and action.description.startswith("filled ")
    and action.count > 0
)

Issue: action.description.startswith("filled ") only matches standard fallback fills, but misses other FreshData imputation algorithms (e.g. MissForest logs step="impute" with description="imputed N missing value(s)...", timeseries logs "interpolated...").
Fix: Check action.step == "impute" or column membership in report.columns_imputed, and verify action.status:

imputed_values = sum(
    action.count
    for action in report.actions
    if (action.step == "impute" or (action.step == "missing" and action.column in report.columns_imputed))
    and getattr(action, "status", "automatic") in {"automatic", "approved"}
    and action.count > 0
)

3. ASCII Quality Report Layout Collapses in Streamlit

Location: examples/integrations/streamlit_app.py:101

with st.expander("Quality report"):
    st.write(report.summary())

Issue: st.write() renders plain text strings as Markdown prose. In Markdown, indentation and single newlines collapse into a single run-on paragraph, flattening the formatted ASCII report tree into an unreadable block.
Fix: Use st.code() or st.text() to preserve monospace layout, indentation, and line breaks:

with st.expander("Quality report"):
    st.code(report.summary(), language="text")

4. Interactive Sidebar Controls for Strategy and Duplicate Removal

Location: examples/integrations/streamlit_app.py:66
Issue: Currently fd.clean(raw_df, return_report=True) hardcodes default options (strategy="balanced", drop_duplicates=False). The demo dataset contains duplicate rows ("Noah Patel"), and FreshData outputs a warning that duplicates were not removed because drop_duplicates=False. As a result, the "Duplicates dropped" metric card always displays 0. Adding interactive sidebar controls showcases the power of an interactive Streamlit app.
Fix:

st.sidebar.header("Cleaning Settings")
strategy = st.sidebar.selectbox("Strategy", ["balanced", "conservative", "aggressive"], index=0)
drop_duplicates = st.sidebar.checkbox("Drop duplicate rows", value=True)

try:
    cleaned_df, report = fd.clean(
        raw_df,
        strategy=strategy,
        drop_duplicates=drop_duplicates,
        return_report=True,
    )

5. Type Annotation & Entrypoint Hygiene

  • In count_modified_columns(report: object), change type annotation to report: Any (import from typing import Any) to pass strict static typecheckers (object has no attributes columns_imputed / actions).
  • Wrap top-level script execution in def main() -> None: with if __name__ == "__main__": main() to avoid top-level side effects when importing functions.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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LGTM! Thanks for addressing the feedback so quickly, @satheesh142002.

All requested improvements are cleanly resolved:

  • Accurate Metric Calculations: count_modified_columns accounts for dropped columns and filters skipped/vetoed actions, and imputed_values inspects action step and imputation metadata rather than fragile string prefixes.
  • ASCII Tree Layout: Monospace formatting and tree indentation in the quality report are preserved using st.code(..., language="text").
  • Interactive Controls: Added sidebar controls for cleaning strategy and drop_duplicates toggling.
  • Script Architecture: Added main() entrypoint guard and updated type annotations.

Approved and ready to merge!

@JohnnyWilson16
JohnnyWilson16 merged commit ba3f01f into FreshCode-Org:main Oct 6, 2026
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feat(examples): add Streamlit interactive data cleaning app recipe

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