notebook-guidance

Notebook Guidance

When to Use a Notebook

Before choosing to use a notebook, evaluate the task complexity using these heuristics.

Use a notebook if you meet at least one of these criteria:

• 📈 Data Insights & Storytelling: Use a notebook for any request to "give insights", "find trends", "explore data", or "analyze data". These tasks benefit from using visualizations to present the data.
• 📊 Visualizations are requested: The user explicitly asks for charts or plots.
• 🔄 Stateful / Iterative Exploration: You need to run a query, inspect results, and decide the next query based on those results while keeping state in memory.

Do NOT use a notebook ONLY if:

• 📝 Simple Fact/Status: The request only requires a single number (e.g., "how many rows") or a status check (e.g., "when was this table updated").
• 🏃‍♂️ Schema Preview: The request is only about the schema or field types.

Golden Rule of Data Storytelling: If any analytical insight, trend, or comparison is involved, favor a notebook and a visualization. A notebook is the "standard" environment for our developer workflow; do not avoid it because of "overhead".

Notebook Best Practices

[!IMPORTANT] Agent execution rules: Your behavior MUST depend on whether the notebook_execute_cell tool is available in your current context:

• If notebook execute_cell tool is available: You MUST follow the incremental GENERATE CELL -> EXECUTE CELL -> VALIDATE flow.
• If notebook execute_cell tool is NOT available: You MUST generate the complete notebook and request user execution.

1. CONDITIONAL EXECUTION FLOW:
   • If notebook execute_cell tool is available: Follow the STEP BY STEP GENERATE CELL -> EXECUTE CELL -> VALIDATE OUTPUT flow. Generate ONE cell, execute it, then verify the output. If the output is data (e.g. a dataframe), you MUST inspect it to confirm the logic is correct before generating the next step. Batch generation of an entire notebook is strictly prohibited because error propagation in notebooks is expensive to fix.
   • If notebook execute_cell tool is NOT available:
     • Create the whole notebook at once.
     • Tell the user to run the notebook.
     • Tell the user to let you know once the notebook run is completed so you can check the outputs to verify it's correct and fix any errors.
2. IDENTIFY DATA EARLY: Use @skill:discovering-gcp-data-assets or BigQuery list tools to find the correct project.dataset.table before writing ANY code. If the table ID is missing, ask the user.
3. CLEAN FINAL STATE: The final notebook MUST NOT have failed cells. If a cell fails, you MUST fix it. If you tried several versions, delete the failed attempts before you present the notebook to the user.
4. LOGICAL CHUNK FIDELITY: Keep cells small. One logical transformation or visualization per cell. Group related cells into logical units (e.g., a BigQuery %%bqsql magic cell followed immediately by a Python visualization cell for those results). Use descriptive markdown cells to separate and document different logical sections.
5. GENERATE VISUALIZATIONS: Always accompany data insights with visualizations; charts are often more effective than raw numbers for communicating trends and comparisons.

Kernel & Environment Management

Notebooks run in specific Kernels (execution backends). You MUST ensure the kernel’s Python environment contains the necessary libraries (bigframes, ipykernel, etc.).

Kernel Types

1. Local Python: Standard Python 3 kernel running on the notebook host (Managed instance, local machine).
2. Cloud Spark Remote (Dataproc Serverless): Transient Spark environment managed by GCP. Use for large-scale data processing.
3. Cloud Spark Remote (Dataproc Cluster): Persistent Spark clusters for shared or custom configurations.
4. Colab (Managed): Ephemeral Google-managed runtimes.

No Active Kernel / Setup Check

1. Infer or Ask about Kernel Preferences:
   • Infer from Context:
     • If the task mentions "Spark", "PySpark", or "distributed compute", or if the active workspace is already a Spark cluster, lean towards Remote Spark.
     • If the task is focused on "BigQuery", "BigFrames", or standard API calls, lean towards Local Python.
   • Ask when Ambiguous: If multiple options fit, ask if they prefer a Local Python or a Cloud/Remote Kernel (e.g., Colab, Spark).
2. For Local Setup: Use @skill:managing-python-dependencies to verify if a virtual environment exists. If not, create one. Ensure ipykernel is installed in that environment. Install any other relevant libraries.
3. For Remote Setup: Advise the user to use the UI to select the appropriate remote kernel.

[!IMPORTANT]

HARD STOP on kernel failure: If a cell execution returns "no active kernel" or any kernel-not-found error, you MUST stop immediately. Do NOT scaffold, generate, or insert any further cells. Inform the user which kernel is needed (e.g., PySpark / Dataproc Serverless) and wait for explicit confirmation that a kernel is active before proceeding with notebook execution.

Proper Library Installation

1. Local Kernels

Before installing any python libraries, you MUST use @skill:managing-python-dependencies to detect how python dependencies are managed in the project.

2. Remote Kernels (Spark/Colab)

Since these are often ephemeral or managed by GCP:

• Check first (REQUIRED): Before writing any %pip install cell, run %pip list or import <package> to confirm the package is not already present. Managed runtimes (Dataproc Serverless, Colab) pre-install many common packages. Only install what is confirmed missing.
• Use %pip install <package> in the first cell if a package is confirmed missing and it's the only way to modify the runtime.

When in doubt about the kernel type or preferred installation method, ask the user for clarification.

Data Analysis & Visualization Rules

Guidelines for performing exploratory data analysis, data cleaning, and visualization in notebooks.

Notebook Layout

The notebook should read like a story. While you have flexibility (e.g., multiple visualizations for one data cell, or data cells building on each other), aim for this general flow:

1. Title & Objective (Markdown Cell)
   • What is this notebook for? (e.g., # Retention Analysis)
2. Section Header (Markdown Cell)
   • What are we looking at now? (e.g., ## Exploring User Retention)
3. Data Acquisition/Transformation (Python cell, may contain %%bqsql magics)
   • Query BigQuery or transform data.
4. Verification (Optional but Recommended) (Python Cell)
   • df.head() or assert sanity checks.
5. Visualization (The Goal) (Python Cell)
   • Plot the insight (e.g., df.plot()).

Repeat steps 2-5 for each new sub-topic or insight. You can have multiple Data cells before a Visualization, or multiple Visualizations from one Data cell. The key is to keep them grouped logically and separated by Markdown headers.

1. Final Summary (Markdown Cell)

   • At the end of the notebook, add a markdown cell containing a summary paragraph that summarizes the findings to the user. The summary MUST follow these guidelines:
   • MUST NOT add Python code to the summary.
   • The summary MUST NOT start with a code block.
   • The summary MUST be strictly grounded in the numerical data verified in the notebook.
   • The summary MUST ONLY contain the following three sections:

     • Q&A If the data analysis task contains questions (implied or

       explicit), you MUST answer them based on the solving process. Skip this section if there are no questions to answer.

     • Data Analysis Key Findings Summarize the key analysis findings

       in bullet points, it's a plus to quote the numbers in the previous steps. Only report high-value findings, skip the obvious ones.

     • Insights or Next Steps Provide 1-2 concise insights or next

       steps in bullet points.

2. Next Steps: After the notebook has been successfully executed and verified, and the summary is complete, notify the user and propose next step suggestions.

Plotting Rules

1. You MUST use different colors for different features to ensure plots are readable for humans.
2. When creating a plot, you MUST adjust the figure size based on the number of features. The labels and legends MUST NOT overlap.
3. You SHOULD arrange the layout wisely. Using subplots CAN help in placing different plots effectively.
4. You MUST use inline figures to present figures and plots along with code and text in the notebook.
5. For clustering, use PCA to reduce to 2D before scatter plotting.
6. Use Line Charts ONLY for continuous data (e.g. time series) where interpolation between points is meaningful.

Data Cleaning Rules

1. You MUST be careful about missing values and duplicated values.
2. You MUST NOT drop columns unless absolutely necessary. Dropping columns is irreversible.
3. You SHOULD focus on columns directly related to accomplishing the task; not every column NEEDS to be cleaned.

Specialized Notebook Guidance

Refer to the following resources for guidance on specific notebook topics:

1. BigQuery in Notebooks

Use BigFrames magics %%bqsql for BigQuery SQL queries. These cells support native BigQuery SQL execution and data export to BigFrames dataframes.

[!IMPORTANT]

• Unless specified by the user, always use SQL for querying BigQuery.
• DO NOT use the standard BigQuery Python client library (google.cloud.bigquery) or pandas.read_gbq.
• Mandatory dataframe export: Always provide a dataframe name e.g. %%bqsql <df_name>. This makes it easy to use results in follow up Python cells.
• Verify that bigframes version number 2.38.0 and above is installed in the notebook runtime environment. If it is missing, ask the user if they would like you to upgrade for them.

Example %%bqsql magic usage:

# Initialize BigFrames and load %%bqsql magics
import bigframes
import bigframes.pandas as bpd
%load_ext bigframes

[!CAUTION] Always use %load_ext bigframes exactly as shown. Do not load submodules — for example, %load_ext bigframes.magics or %load_ext bigframes.bigquery are not valid and must not be used.

[!IMPORTANT] The bigframes library must be installed. Determine if bigframes needs to be installed by following @skill:managing-python-dependencies.

%%bqsql df_sample
SELECT * FROM `project.dataset.table` LIMIT 10

Anti-patterns (NEVER DO THESE)

[!CAUTION] 1. NO Python SDK for Queries: Do not switch to client.query(sql).to_dataframe() if SQL fails. Fix the SQL syntax instead. 2. NO Mixing Logic: Do not put Python code in the same cell as %%bqsql magics.

Working with SQL Results in Python

Magic cells with %%bqsql <df_name> produce a BigQuery DataFrame. In subsequent cells, you can use <df_name> directly.

[!IMPORTANT] You MUST use BigFrames for data exploration, manipulation, splitting etc. You MUST use BQML SQL or bigframes.ml for machine learning tasks. You MUST NOT use pandas or Scikit-learn.

BigQuery DataFrame Tips

• Avoid .to_pandas(): You MUST NOT use .to_pandas() to download the entire dataset into memory. There are some exceptions:
  • An error message explicitly requests you to use to_pandas()
  • You are going to visualize the data, and the visualization library does not accept BigFrames Dataframe/Series instances. In this case, reduce the amount of data you are going to download before calling .to_pandas()
• Avoid read_gbq() for SQL: Do not write SQL queries and execute them with read_gbq(). Use BigFrames Dataframe/Series methods instead.
• Use BigFrames ML package for Machine Learning Tasks: Do not use Scikit-learn or other ML libraries with BigFrames dataframes. Import your tools/classes from bigframes.ml.
• Stay in the Cloud: Perform data cleaning, transformation, and analysis via BigFrames methods to leverage BigQuery's scale.
• Accessors over UDFs/Lambdas:
  • Prefer built-in accessors (e.g., df.col.str.*, df.col.dt.*) over remote UDFs.
  • Do not use lambdas with Series.map() or DataFrame.apply().
• Schema Verification: Do not assume schema of intermediate outputs. Check .dtypes after loading, and use display() with .head() or .peek().
• Visualization: BigFrames Dataframe mostly works directly with Matplotlib, Seaborn, and other plotting libraries. If your attempt didn't work, try using the "plot" accessor. If that didn't work either, you MUST sample or aggregate your data to make it small enough before calling "to_pandas()".
• Model Persistence: To persist a model. use model.to_gbq(). To load a persisted model, use bpd.read_gbq_model().

2. Machine Learning in Notebooks

Integration with machine learning workflows and best practices. - Guide: Use @skill:ml-best-practices. - MUST READ WHEN: The task involves machine learning, training a model, clustering, classification, regression, or time-series forecasting.

If any "MUST READ WHEN" condition is met, you MUST read the corresponding guide before proceeding.