Spark: display() function

The display() function is commonly used in Databricks notebooks to render DataFrames, charts, and other visualizations in an interactive and user-friendly format. It is not a native Spark function but is specific to Databricks. The display() function provides a rich set of features for data exploration, including tabular views, charts, and custom visualizations.

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1. Syntax

• Databricks:
  display(df)
  
• PySpark (outside Databricks):
  • Use df.show() or df.toPandas() for similar functionality.

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2. Key Features

• Interactive Tables: Displays DataFrames in an interactive table with sorting, filtering, and pagination.
• Visualizations: Supports built-in charts (e.g., bar charts, line charts, pie charts) for data exploration.
• Custom Visualizations: Allows custom visualizations using libraries like Matplotlib, Plotly, or Seaborn.
• Rich Output: Can display images, HTML, and other rich content.

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3. Examples

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Example 1: Displaying a DataFrame as a Table

• Databricks:
  from pyspark.sql import SparkSession
  
  spark = SparkSession.builder.appName("DisplayExample").getOrCreate()
  
  # Create DataFrame
  data = [("Anand", 25, 3000), ("Bala", 30, 4000), ("Kavitha", 28, 3500), ("Raj", 35, 4500)]
  columns = ["Name", "Age", "Salary"]
  
  df = spark.createDataFrame(data, columns)
  
  # Display the DataFrame
  display(df)
  

Output:

• An interactive table with columns Name, Age, and Salary.

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Example 2: Displaying a Chart

• Databricks:
  # Display a bar chart of Salary by Name
  display(df)
  
  • After running the above code, click on the Chart button in the Databricks notebook to visualize the data as a bar chart.

Output:

• A bar chart showing Salary on the y-axis and Name on the x-axis.

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Example 3: Displaying a Pie Chart

• Databricks:
  # Display a pie chart of Age distribution
  display(df)
  
  • After running the above code, click on the Chart button and select Pie Chart to visualize the data.

Output:

• A pie chart showing the distribution of Age.

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Example 4: Displaying Custom Visualizations

• Databricks:
  import matplotlib.pyplot as plt
  import pandas as pd
  
  # Convert Spark DataFrame to Pandas DataFrame
  pandas_df = df.toPandas()
  
  # Create a custom bar chart
  plt.bar(pandas_df["Name"], pandas_df["Salary"])
  plt.xlabel("Name")
  plt.ylabel("Salary")
  plt.title("Salary by Name")
  plt.show()
  
  # Display the chart
  display()
  

Output:

• A custom bar chart created using Matplotlib.

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Example 5: Displaying a DataFrame with Filters

• Databricks:
  # Display the DataFrame with filters
  display(df)
  
  • After running the above code, use the filter options in the interactive table to filter rows.

Output:

• An interactive table with filter options.

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Example 6: Displaying a Line Chart

• Databricks:
  # Display a line chart of Salary by Age
  display(df)
  
  • After running the above code, click on the Chart button and select Line Chart to visualize the data.

Output:

• A line chart showing Salary on the y-axis and Age on the x-axis.

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Example 7: Displaying HTML Content

• Databricks:
  # Display HTML content
  html_content = "<h1>Hello, Databricks!</h1>"
  displayHTML(html_content)
  

Output:

• Rendered HTML content in the notebook.

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4. Common Use Cases

• Exploring and analyzing data interactively in Databricks notebooks.
• Creating visualizations for data insights and reporting.
• Sharing results with stakeholders in a user-friendly format.

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5. Performance Considerations

• display() is optimized for Databricks notebooks and works efficiently with large datasets.
• Use it judiciously for very wide DataFrames (many columns), as it processes all specified columns.

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6. Key Takeaways

1. Purpose: The display() function is used in Databricks notebooks to render DataFrames, charts, and visualizations interactively.
2. Interactive Tables: Provides sorting, filtering, and pagination for DataFrames.
3. Visualizations: Supports built-in charts and custom visualizations.
4. Common Use Cases:
   • Exploring and analyzing data interactively.
   • Creating visualizations for data insights.
   • Sharing results in a user-friendly format.
5. Performance: display() is optimized for Databricks notebooks and works efficiently with large datasets.