docs(bigquery/bigframes): add load_table_dataframe code sample

[shuoweil]

Description

Adds a BigQuery DataFrames (bigframes) code sample demonstrating how to load a pandas DataFrame into a BigQuery table, targeting the documentation page bigquery-load-table-dataframe.

Fixes b/546158350 (Subtask of b/522898394)

Summary of Changes

• Added bigquery/bigframes/load_table_dataframe.py demonstrating converting a local pandas DataFrame to BigQuery DataFrames and writing to BigQuery using to_gbq.
• Added corresponding unit test load_table_dataframe_test.py.

[snippet-bot]

Here is the summary of changes.

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• bigquery/bigframes/load_table_dataframe.py:15, tag bigquery_bigframes_load_table_dataframe

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[gemini-code-assist]

Code Review

This pull request introduces a new script and associated test to demonstrate loading a local pandas DataFrame into a BigQuery table using BigQuery DataFrames. The review feedback recommends replacing the deprecated pytz library with the standard library's zoneinfo module for cleaner and more modern timezone handling.

[gemini-code-assist]

Since Python 3.9, the standard library includes the zoneinfo module, which is the modern and recommended way to handle time zones. Using zoneinfo avoids the need for the external pytz library, which is deprecated and has known quirks (such as requiring the .localize() method instead of passing the timezone directly to the datetime constructor).

Suggested change

	import pytz
	from zoneinfo import ZoneInfo

[gemini-code-assist]

Use standard library zoneinfo.ZoneInfo and datetime.timezone.utc instead of pytz to localize the datetimes. This is cleaner, more idiomatic, and avoids the deprecated pytz library.

    records = [
        {
            "title": "The Meaning of Life",
            "release_year": 1983,
            "length_minutes": 112.5,
            "release_date": datetime.datetime(
                1983, 5, 9, 13, 0, 0, tzinfo=ZoneInfo("Europe/Paris")
            ).astimezone(datetime.timezone.utc),
            # Assume UTC timezone when a datetime object contains no timezone.
            "dvd_release": datetime.datetime(2002, 1, 22, 7, 0, 0),
        },
        {
            "title": "Monty Python and the Holy Grail",
            "release_year": 1975,
            "length_minutes": 91.5,
            "release_date": datetime.datetime(
                1975, 4, 9, 23, 59, 2, tzinfo=ZoneInfo("Europe/London")
            ).astimezone(datetime.timezone.utc),
            "dvd_release": datetime.datetime(2002, 7, 16, 9, 0, 0),
        },
        {
            "title": "Life of Brian",
            "release_year": 1979,
            "length_minutes": 94.25,
            "release_date": datetime.datetime(
                1979, 8, 17, 23, 59, 5, tzinfo=ZoneInfo("America/New_York")
            ).astimezone(datetime.timezone.utc),
            "dvd_release": datetime.datetime(2008, 1, 14, 8, 0, 0),
        },
        {
            "title": "And Now for Something Completely Different",
            "release_year": 1971,
            "length_minutes": 88.0,
            "release_date": datetime.datetime(
                1971, 9, 28, 23, 59, 7, tzinfo=ZoneInfo("Europe/London")
            ).astimezone(datetime.timezone.utc),
            "dvd_release": datetime.datetime(2003, 10, 22, 10, 0, 0),
        },
    ]

[shuoweil]

Will check in the code change in Git-on-Borg.