学ぶ Selecting, Filtering, and Renaming Columns

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The three most common DataFrame operations are selecting the columns you need, filtering rows by condition, and renaming columns for clarity. These map directly to SQL SELECT, WHERE, and AS.

Selecting Columns


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import urllib.request
from pyspark.sql import SparkSession

urllib.request.urlretrieve(
    "https://staging-content-media-cdn.codefinity.com/courses/aa80ac56-0d50-49e8-9231-2c2374cd3e9d/flights.csv",
    "flights.csv"
)

spark = SparkSession.builder \
    .appName("SelectFilterRename") \
    .master("local[*]") \
    .getOrCreate()

flights_df = spark.read.csv("flights.csv", header=True, inferSchema=True)

# Selecting specific columns
flights_df.select("AIRLINE", "ORIGIN_AIRPORT", "DESTINATION_AIRPORT", "DEPARTURE_DELAY").show(5)

Filtering Rows


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from pyspark.sql.functions import col

# Filtering flights with arrival delay over 60 minutes
delayed_df = flights_df.filter(col("ARRIVAL_DELAY") > 60)

# Combining conditions
long_delayed_df = flights_df.filter(
    (col("ARRIVAL_DELAY") > 60) & (col("DISTANCE") > 1000)
)

long_delayed_df.select("AIRLINE", "ORIGIN_AIRPORT", "DESTINATION_AIRPORT", "ARRIVAL_DELAY", "DISTANCE").show(5)

Use col() from pyspark.sql.functions for conditions – it is more explicit and avoids ambiguity when working with multiple DataFrames.

Renaming Columns


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# Renaming columns for readability
renamed_df = flights_df \
    .withColumnRenamed("ORIGIN_AIRPORT", "FROM") \
    .withColumnRenamed("DESTINATION_AIRPORT", "TO") \
    .withColumnRenamed("ARRIVAL_DELAY", "DELAY_MINUTES")

renamed_df.select("AIRLINE", "FROM", "TO", "DELAY_MINUTES").show(5)

Adding a Derived Column


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from pyspark.sql.functions import col

# Adding a boolean column indicating whether the flight was significantly delayed
flights_df = flights_df.withColumn(
    "IS_DELAYED",
    col("ARRIVAL_DELAY") > 15
)

flights_df.select("AIRLINE", "ARRIVAL_DELAY", "IS_DELAYED").show(5)

すべて明確でしたか？

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セクション 1. 章 9

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セクション 1. 章 9