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🐍 πŸ“„ PySpark Cheat Sheet

A quick reference guide to the most commonly used patterns and functions in PySpark SQL.

Table of Contents

If you can't find what you're looking for, check out the PySpark Official Documentation and add it here!

Quickstart

Install on macOS:

brew install apache-spark && pip install pyspark

Create your first DataFrame:

from pyspark.sql import SparkSession

spark = SparkSession.builder.getOrCreate()

# I/O options: https://spark.apache.org/docs/latest/api/python/reference/pyspark.sql/io.html
df = spark.read.csv('/path/to/your/input/file')

Basics

# Show a preview
df.show()

# Show preview of first / last n rows
df.head(5)
df.tail(5)

# Show preview as JSON (WARNING: in-memory)
df = df.limit(10) # optional
print(json.dumps([row.asDict(recursive=True) for row in df.collect()], indent=2))

# Limit actual DataFrame to n rows (non-deterministic)
df = df.limit(5)

# Get columns
df.columns

# Get columns + column types
df.dtypes

# Get schema
df.schema

# Get row count
df.count()

# Get column count
len(df.columns)

# Write output to disk
df.write.csv('/path/to/your/output/file')

# Get results (WARNING: in-memory) as list of PySpark Rows
df = df.collect()

# Get results (WARNING: in-memory) as list of Python dicts
dicts = [row.asDict(recursive=True) for row in df.collect()]

# Convert (WARNING: in-memory) to Pandas DataFrame
df = df.toPandas()

Common Patterns

Importing Functions & Types

# Easily reference these as F.my_function() and T.my_type() below
from pyspark.sql import functions as F, types as T

Filtering

# Filter on equals condition
df = df.filter(df.is_adult == 'Y')

# Filter on >, <, >=, <= condition
df = df.filter(df.age > 25)

# Multiple conditions require parentheses around each condition
df = df.filter((df.age > 25) & (df.is_adult == 'Y'))

# Compare against a list of allowed values
df = df.filter(col('first_name').isin([3, 4, 7]))

# Sort results
df = df.orderBy(df.age.asc()))
df = df.orderBy(df.age.desc()))

Joins

# Left join in another dataset
df = df.join(person_lookup_table, 'person_id', 'left')

# Match on different columns in left & right datasets
df = df.join(other_table, df.id == other_table.person_id, 'left')

# Match on multiple columns
df = df.join(other_table, ['first_name', 'last_name'], 'left')

Column Operations

# Add a new static column
df = df.withColumn('status', F.lit('PASS'))

# Construct a new dynamic column
df = df.withColumn('full_name', F.when(
    (df.fname.isNotNull() & df.lname.isNotNull()), F.concat(df.fname, df.lname)
).otherwise(F.lit('N/A'))

# Pick which columns to keep, optionally rename some
df = df.select(
    'name',
    'age',
    F.col('dob').alias('date_of_birth'),
)

# Remove columns
df = df.drop('mod_dt', 'mod_username')

# Rename a column
df = df.withColumnRenamed('dob', 'date_of_birth')

# Keep all the columns which also occur in another dataset
df = df.select(*(F.col(c) for c in df2.columns))

# Batch Rename/Clean Columns
for col in df.columns:
    df = df.withColumnRenamed(col, col.lower().replace(' ', '_').replace('-', '_'))

Casting & Coalescing Null Values & Duplicates

# Cast a column to a different type
df = df.withColumn('price', df.price.cast(T.DoubleType()))

# Replace all nulls with a specific value
df = df.fillna({
    'first_name': 'Tom',
    'age': 0,
})

# Take the first value that is not null
df = df.withColumn('last_name', F.coalesce(df.last_name, df.surname, F.lit('N/A')))

# Drop duplicate rows in a dataset (distinct)
df = df.dropDuplicates() # or
df = df.distinct()

# Drop duplicate rows, but consider only specific columns
df = df.dropDuplicates(['name', 'height'])

# Replace empty strings with null (leave out subset keyword arg to replace in all columns)
df = df.replace({"": None}, subset=["name"])

# Convert Python/PySpark/NumPy NaN operator to null
df = df.replace(float("nan"), None)

String Operations

String Filters

# Contains - col.contains(string)
df = df.filter(df.name.contains('o'))

# Starts With - col.startswith(string)
df = df.filter(df.name.startswith('Al'))

# Ends With - col.endswith(string)
df = df.filter(df.name.endswith('ice'))

# Is Null - col.isNull()
df = df.filter(df.is_adult.isNull())

# Is Not Null - col.isNotNull()
df = df.filter(df.first_name.isNotNull())

# Like - col.like(string_with_sql_wildcards)
df = df.filter(df.name.like('Al%'))

# Regex Like - col.rlike(regex)
df = df.filter(df.name.rlike('[A-Z]*ice$'))

# Is In List - col.isin(*cols)
df = df.filter(df.name.isin('Bob', 'Mike'))

String Functions

# Substring - col.substr(startPos, length)
df = df.withColumn('short_id', df.id.substr(0, 10))

# Trim - F.trim(col)
df = df.withColumn('name', F.trim(df.name))

# Left Pad - F.lpad(col, len, pad)
# Right Pad - F.rpad(col, len, pad)
df = df.withColumn('id', F.lpad('id', 4, '0'))

# Left Trim - F.ltrim(col)
# Right Trim - F.rtrim(col)
df = df.withColumn('id', F.ltrim('id'))

# Concatenate - F.concat(*cols)
df = df.withColumn('full_name', F.concat('fname', F.lit(' '), 'lname'))

# Concatenate with Separator/Delimiter - F.concat_ws(delimiter, *cols)
df = df.withColumn('full_name', F.concat_ws('-', 'fname', 'lname'))

# Regex Replace - F.regexp_replace(str, pattern, replacement)[source]
df = df.withColumn('id', F.regexp_replace(id, '0F1(.*)', '1F1-$1'))

# Regex Extract - F.regexp_extract(str, pattern, idx)
df = df.withColumn('id', F.regexp_extract(id, '[0-9]*', 0))

Number Operations

# Round - F.round(col, scale=0)
df = df.withColumn('price', F.round('price', 0))

# Floor - F.floor(col)
df = df.withColumn('price', F.floor('price'))

# Ceiling - F.ceil(col)
df = df.withColumn('price', F.ceil('price'))

# Absolute Value - F.abs(col)
df = df.withColumn('price', F.abs('price'))

# X raised to power Y – F.pow(x, y)
df = df.withColumn('exponential_growth', F.pow('x', 'y'))

# Select smallest value out of multiple columns – F.least(*cols)
df = df.withColumn('least', F.least('subtotal', 'total'))

# Select largest value out of multiple columns – F.greatest(*cols)
df = df.withColumn('greatest', F.greatest('subtotal', 'total'))

Date & Timestamp Operations

# Add a column with the current date
df = df.withColumn('current_date', F.current_date())

# Convert a string of known format to a date (excludes time information)
df = df.withColumn('date_of_birth', F.to_date('date_of_birth', 'yyyy-MM-dd'))

# Convert a string of known format to a timestamp (includes time information)
df = df.withColumn('time_of_birth', F.to_timestamp('time_of_birth', 'yyyy-MM-dd HH:mm:ss'))

# Get year from date:       F.year(col)
# Get month from date:      F.month(col)
# Get day from date:        F.dayofmonth(col)
# Get hour from date:       F.hour(col)
# Get minute from date:     F.minute(col)
# Get second from date:     F.second(col)
df = df.filter(F.year('date_of_birth') == F.lit('2017'))

# Add & subtract days
df = df.withColumn('three_days_after', F.date_add('date_of_birth', 3))
df = df.withColumn('three_days_before', F.date_sub('date_of_birth', 3))

# Add & Subtract months
df = df.withColumn('next_month', F.add_month('date_of_birth', 1))

# Get number of days between two dates
df = df.withColumn('days_between', F.datediff('start', 'end'))

# Get number of months between two dates
df = df.withColumn('months_between', F.months_between('start', 'end'))

# Keep only rows where date_of_birth is between 2017-05-10 and 2018-07-21
df = df.filter(
    (F.col('date_of_birth') >= F.lit('2017-05-10')) &
    (F.col('date_of_birth') <= F.lit('2018-07-21'))
)

Array Operations

# Column Array - F.array(*cols)
df = df.withColumn('full_name', F.array('fname', 'lname'))

# Empty Array - F.array(*cols)
df = df.withColumn('empty_array_column', F.array([]))

# Get element at index – col.getItem(n)
df = df.withColumn('first_element', F.col("my_array").getItem(0))

# Array Size/Length – F.size(col)
df = df.withColumn('array_length', F.size('my_array'))

# Flatten Array – F.flatten(col)
df = df.withColumn('flattened', F.flatten('my_array'))

# Unique/Distinct Elements – F.array_distinct(col)
df = df.withColumn('unique_elements', F.array_distinct('my_array'))

# Map over & transform array elements – F.transform(col, func: col -> col)
df = df.withColumn('elem_ids', F.transform(F.col('my_array'), lambda x: x.getField('id')))

# Return a row per array element – F.explode(col)
df = df.select(F.explode('my_array'))

Struct Operations

# Make a new Struct column (similar to Python's `dict()`) – F.struct(*cols)
df = df.withColumn('my_struct', F.struct(F.col('col_a'), F.col('col_b')))

# Get item from struct by key – col.getField(str)
df = df.withColumn('col_a', F.col('my_struct').getField('col_a'))

Aggregation Operations

# Row Count:                F.count()
# Sum of Rows in Group:     F.sum(*cols)
# Mean of Rows in Group:    F.mean(*cols)
# Max of Rows in Group:     F.max(*cols)
# Min of Rows in Group:     F.min(*cols)
# First Row in Group:       F.alias(*cols)
df = df.groupBy('gender').agg(F.max('age').alias('max_age_by_gender'))

# Collect a Set of all Rows in Group:       F.collect_set(col)
# Collect a List of all Rows in Group:      F.collect_list(col)
df = df.groupBy('age').agg(F.collect_set('name').alias('person_names'))

# Just take the lastest row for each combination (Window Functions)
from pyspark.sql import Window as W

window = W.partitionBy("first_name", "last_name").orderBy(F.desc("date"))
df = df.withColumn("row_number", F.row_number().over(window))
df = df.filter(F.col("row_number") == 1)
df = df.drop("row_number")

Advanced Operations

Repartitioning

# Repartition – df.repartition(num_output_partitions)
df = df.repartition(1)

UDFs (User Defined Functions

# Multiply each row's age column by two
times_two_udf = F.udf(lambda x: x * 2)
df = df.withColumn('age', times_two_udf(df.age))

# Randomly choose a value to use as a row's name
import random

random_name_udf = F.udf(lambda: random.choice(['Bob', 'Tom', 'Amy', 'Jenna']))
df = df.withColumn('name', random_name_udf())

Useful Functions / Transformations

def flatten(df: DataFrame, delimiter="_") -> DataFrame:
    '''
    Flatten nested struct columns in `df` by one level separated by `delimiter`, i.e.:

    df = [ {'a': {'b': 1, 'c': 2} } ]
    df = flatten(df, '_')
    -> [ {'a_b': 1, 'a_c': 2} ]
    '''
    flat_cols = [name for name, type in df.dtypes if not type.startswith("struct")]
    nested_cols = [name for name, type in df.dtypes if type.startswith("struct")]

    flat_df = df.select(
        flat_cols
        + [F.col(nc + "." + c).alias(nc + delimiter + c) for nc in nested_cols for c in df.select(nc + ".*").columns]
    )
    return flat_df


def lookup_and_replace(df1, df2, df1_key, df2_key, df2_value):
    '''
    Replace every value in `df1`'s `df1_key` column with the corresponding value
    `df2_value` from `df2` where `df1_key` matches `df2_key`

    df = lookup_and_replace(people, pay_codes, id, pay_code_id, pay_code_desc)
    '''
    return (
        df1
        .join(df2[[df2_key, df2_value]], df1[df1_key] == df2[df2_key], 'left')
        .withColumn(df1_key, F.coalesce(F.col(df2_value), F.col(df1_key)))
        .drop(df2_key)
        .drop(df2_value)
    )