display

laktory.narwhals_ext.dataframe.display

FUNCTION	DESCRIPTION
display	Prints the first n rows to the console. Compatible for both static and

display(self, n=10, timeout=None, truncate=False, vertical=False, refresh_interval=3.0)

Prints the first n rows to the console. Compatible for both static and streaming dataframes. In the case of a streaming dataframe, console will be continuously updated until there is a keyboard input.

PARAMETER	DESCRIPTION
n	Number of rows to display TYPE: int DEFAULT: 10
truncate	If set to True, truncate strings longer than 20 chars by default. If set to a number greater than one, truncates long strings to length truncate and align cells right. TYPE: bool | int DEFAULT: False
vertical	If set to True, print output rows vertically (one line per column value). TYPE: bool DEFAULT: False
refresh_interval	Pause duration, in seconds, between each update for streaming dataframes TYPE: float DEFAULT: 3.0

RETURNS	DESCRIPTION
None	None

Examples:

import narwhals as nw
import pandas as pd

import laktory as lk  # noqa: F401

spark = lk.get_spark_session()
df = nw.from_native(
    spark.createDataFrame(
        pd.DataFrame(
            {
                "symbol": ["AAPL", "GOOGL"],
                "price": [200.0, 205.0],
                "tstamp": ["2023-09-01", "2023-09-01"],
            }
        )
    )
)
df.laktory.display(n=5, refresh_interval=2)

Source code in laktory/narwhals_ext/dataframe/display.py

def display(
    self,
    n: int = 10,
    timeout: int | None = None,
    truncate: bool | int = False,
    vertical: bool = False,
    refresh_interval: float = 3.0,
) -> None:
    """
    Prints the first n rows to the console. Compatible for both static and
    streaming dataframes. In the case of a streaming dataframe, console will
    be continuously updated until there is a keyboard input.

    Parameters
    ----------
    n:
        Number of rows to display
    truncate:
        If set to `True`, truncate strings longer than 20 chars by default. If
        set to a number greater than one, truncates long strings to length
        truncate and align cells right.
    vertical:
        If set to `True`, print output rows vertically (one line per column
        value).
    refresh_interval:
        Pause duration, in seconds, between each update for streaming
        dataframes


    Returns
    -------
    :
        None

    Examples
    --------

    ```py
    import narwhals as nw
    import pandas as pd

    import laktory as lk  # noqa: F401

    spark = lk.get_spark_session()
    df = nw.from_native(
        spark.createDataFrame(
            pd.DataFrame(
                {
                    "symbol": ["AAPL", "GOOGL"],
                    "price": [200.0, 205.0],
                    "tstamp": ["2023-09-01", "2023-09-01"],
                }
            )
        )
    )
    df.laktory.display(n=5, refresh_interval=2)
    ```
    """

    backend = DataFrameBackends.from_df(self._df)
    df = self._df.to_native()
    if backend == DataFrameBackends.PYSPARK:
        if not df.isStreaming:
            df.show(n=n, truncate=truncate, vertical=vertical)

        else:
            # Start the streaming query
            query = (
                df.writeStream.outputMode("append")
                .format("memory")  # Store the results in-memory table
                .queryName("_laktory_tmp_view")
                .trigger(availableNow=True)
                .start()
            )
            t0 = time.time()
            try:
                while True:
                    # Fetch and display the latest rows
                    df.sparkSession.sql(
                        f"SELECT * FROM _laktory_tmp_view LIMIT {n}"
                    ).show(truncate=truncate, vertical=vertical)
                    time.sleep(refresh_interval)
                    if timeout:
                        dt = time.time() - t0
                        if dt > timeout:
                            break
            except KeyboardInterrupt:
                print("Stopped streaming display.")
            finally:
                query.stop()

    elif backend == DataFrameBackends.POLARS:
        import polars as pl

        df = df.limit(n)
        if isinstance(df, pl.LazyFrame):
            df = df.collect()
        print(df)
        print(f"only showing top {n} rows")
    else:
        raise NotImplementedError(f"Display not supported for {backend}")