nxcals.api.extraction.data.builders.DataFrame.columns

property DataFrame.columns: List[str]

Retrieves the names of all columns in the DataFrame as a list.

The order of the column names in the list reflects their order in the DataFrame.

New in version 1.3.0.

Changed in version 3.4.0: Supports Spark Connect.

Returns:

List of column names in the DataFrame.

Return type:

list

Examples

Example 1: Retrieve column names of a DataFrame

>>> df = spark.createDataFrame(
...     [(14, "Tom", "CA"), (23, "Alice", "NY"), (16, "Bob", "TX")],
...     ["age", "name", "state"]
... )
>>> df.columns
['age', 'name', 'state']

Example 2: Using column names to project specific columns

>>> selected_cols = [col for col in df.columns if col != "age"]
>>> df.select(selected_cols).show()
+-----+-----+
| name|state|
+-----+-----+
|  Tom|   CA|
|Alice|   NY|
|  Bob|   TX|
+-----+-----+

Example 3: Checking if a specific column exists in a DataFrame

>>> "state" in df.columns
True
>>> "salary" in df.columns
False

Example 4: Iterating over columns to apply a transformation

>>> import pyspark.sql.functions as f
>>> for col_name in df.columns:
...     df = df.withColumn(col_name, f.upper(f.col(col_name)))
>>> df.show()
+---+-----+-----+
|age| name|state|
+---+-----+-----+
| 14|  TOM|   CA|
| 23|ALICE|   NY|
| 16|  BOB|   TX|
+---+-----+-----+

Example 5: Renaming columns and checking the updated column names

>>> df = df.withColumnRenamed("name", "first_name")
>>> df.columns
['age', 'first_name', 'state']

Example 6: Using the columns property to ensure two DataFrames have the same columns before a union

>>> df2 = spark.createDataFrame(
...     [(30, "Eve", "FL"), (40, "Sam", "WA")], ["age", "name", "location"])
>>> df.columns == df2.columns
False