c++ select函數_PySpark 操作函數一覽

PySpark 操作函數一覽

Created: Sep 14, 2020 10:28 AM Tags: Big Data, PySpark, Python, Spark

Pyspark.sql.functions

from pyspark.sql import functions as F

函數使用說明

基本數學函數類

abs
sin、cos、tan、asin、acos 、atan、sinh、cosh、tanh
ceil、round、floor
exp、log、log2、pow、sqrt、cbrt
factorial

特定類型

日期

current_date、current_timestamp、add_months、unix_timestamp

df = spark.createDataFrame([('2015-04-08',)], ['dt']
df.select(F.add_months(df.dt, 1).alias('next_month'))""""
+----------+
|next_month|
+----------+
|2015-05-08|
+----------+
"""

add_months、date_add、date_format、date_sub、date_trunc、date_diff
dayofmonth、dayofweek、dayofyear、weekofyear
hour、last_day、minute、month、months_between、next_day、year

字符

ascii、substring、substring_index
base64、unbase64
decode、encode
expr、conv
format_string
length
lower、upper
reverse
size

Binary

bin、bitwiseNOT、
hash、md5、sha1、sha2
hex、unhex

角度

toDegrees、toRadians、radians

數字

format_number

判斷

isnan、isnull

統計計算

avg、corr、count、countDistinct、cume_dist
greatest、kurtosis、variance
max、min、mean、rand、randn、rank
skewness、sum、sumDistinct

數組處理

flatten、slice、element_at、array_contains、array_distinct、array_except、array_intersect、array_join、array_max、array_min、array_position、array_remove、array_repeat、array_sort、array_union、arrays_overlap、arrays_zip

# 數組列包含元素
df = spark.createDataFrame([(["a", "b", "c"],), ([],)], ['data'])
df.withColumn("array_contains", F.array_contains(df.data, "a")).show()"""
+---------+--------------+
|     data|array_contains|
+---------+--------------+
|[a, b, c]|          true|
|       []|         false|
+---------+--------------+
"""

數組函數說明

df = spark.createDataFrame([(([1, 2, 3], [2, 3, 4]))], ['vals1', 'vals2'])
df.show()
df_new = df.select(F.arrays_zip(df.vals1, df.vals2).alias('zipped'))
df_new.show()
row = df_new.collect()[0]
row['zipped'][0]['vals1'] == row['zipped'][0][0] == 1"""
+---------+---------+
|    vals1|    vals2|
+---------+---------+
|[1, 2, 3]|[2, 3, 4]|
+---------+---------++--------------------+
|              zipped|
+--------------------+
|[[1, 2], [2, 3], ...|
+--------------------+True
"""

列處理

coalesce

df = spark.createDataFrame([(None, None), (1, None), (None, 2)], ("a", "b"))
df.show()
df.withColumn('coalesce', F.coalesce(df.a, df.b)).show()"""
+----+----+
|   a|   b|
+----+----+
|null|null|
|   1|null|
|null|   2|
+----+----++----+----+--------+
|   a|   b|coalesce|
+----+----+--------+
|null|null|    null|
|   1|null|       1|
|null|   2|       2|
+----+----+--------+
"""

array

# 多列數據合并成單獨一列數組
df = spark.createDataFrame([('2015-04-08', 1, )], ['dt', 'int'])
df.select(F.array([df.dt, df.int]).alias("arr")).show()"""
+---------------+
|            arr|
+---------------+
|[2015-04-08, 1]|
+---------------+
"""

concat、concat_ws

df = spark.createDataFrame([('abcd','123')], ['s', 'd'])
df.withColumn('concat', F.concat_ws('-', df.s, df.d).alias('s')).show()
"""
+----+---+--------+
|   s|  d|  concat|
+----+---+--------+
|abcd|123|abcd-123|
+----+---+--------+
"""

col、column、lit

df = spark.createDataFrame([(11, 12), (21, 22), (31, 32)], ("a", "b"))
df.withColumn('a+100', F.col('a')  + F.lit(100)).show()"""
+---+---+-----+
|  a|  b|a+100|
+---+---+-----+
| 11| 12|  111|
| 21| 22|  121|
| 31| 32|  131|
+---+---+-----+
"""

explode、explode_outer、posexplode、posexplode_outer

# 將 array/map 展開成新 dataframe 的行df = spark.createDataFrame([(1,2,3)], ArrayType(IntegerType()))
df.select(F.explode(df.value).alias("int")).show()"""
+---+
|int|
+---+
|  1|
|  2|
|  3|
+---+
"""df = spark.createDataFrame([({'a': 1, 'b': 2})], MapType(StringType(), IntegerType()))
df.select(F.explode(df.value).alias('key', 'value')).show()"""
+---+-----+
|key|value|
+---+-----+
|  a|    1|
|  b|    2|
+---+-----+
"""

from_csv、from_json、get_json_object

# 從 json string 提取對應的字段并擴展成列
import json
data = {'a': 1, 'b': [1,2,3]}
data_s = json.dumps(data)schema = StructType([StructField('a', IntegerType(), True),StructField('b', ArrayType(IntegerType()), True)
])df= spark.createDataFrame([(data_s)], schema=StringType())
df.show()"""
+--------------------+
|               value|
+--------------------+
|{"a": 1, "b": [1,...|
+--------------------+
"""df_from_json = df.withColumn('json', F.from_json(df.value, schema=schema))df_from_json.select(df_from_json.value, df_from_json.json.a.alias('value.a'), df_from_json.json.b.alias('value.b')
).show()"""
+--------------------+-------+---------+
|               value|value.a|  value.b|
+--------------------+-------+---------+
|{"a": 1, "b": [1,...|      1|[1, 2, 3]|
+--------------------+-------+---------+
"""
data = [("1", '''{"f1": "value1", "f2": "value2"}'''), ("2", '''{"f1": "value12"}''')]
df = spark.createDataFrame(data, ("key", "jstring"))
df.select(df.key, F.get_json_object(df.jstring, '$.f1').alias("c0"), F.get_json_object(df.jstring, '$.f2').alias("c1") ).show()"""
---+-------+------+
|key|     c0|    c1|
+---+-------+------+
|  1| value1|value2|
|  2|value12|  null|
+---+-------+------+
"""

create_map、map_from_arrays、map_from_entries、map_concat、map_keys、map_values、map_entries

df = spark.createDataFrame([([2, 5], ['a', 'b'])], ['k', 'v'])
df.select(F.map_from_arrays(df.k, df.v).alias("map")).show()"""
+----------------+
|             map|
+----------------+
|[2 -> a, 5 -> b]|
+----------------+
"""

regexp_extract、regexp_replace

# 正則提取與正則替換
df = spark.createDataFrame([('100-200',)], ['str'])
df.select('str', F.regexp_extract('str', r'(d+)-(d+)', 1).alias('first'),F.regexp_replace('str', r'(d+)-(d+)', "$2-$1").alias('swap'),
).show()"""
+-------+-----+-------+
|    str|first|   swap|
+-------+-----+-------+
|100-200|  100|200-100|
+-------+-----+-------+
"""

udf

Pyspark.sql.types

Base 類型

DataType

基本類型

NullType
StringType
BinaryType
BooleanType
DateType
TimestampType
DecimalType
DoubleType
FloatType
ByteType
IntegerType
LongType
ShortType

疊加類型

`ArrayType`

df = spark.createDataFrame([([1,2,3])], schema=ArrayType(IntegerType()) )
df.show()
# +---------+
# |    value|
# +---------+
# |[1, 2, 3]|
# +---------+df.collect()[0].value[0]
# 1
# 默認的 column name 為 value

`MapType`

df = spark.createDataFrame([({'a': 1, 'b': 2})], schema=MapType(StringType(), IntegerType()) )
df.show()
# +----------------+
# |           value|
# +----------------+
# |[a -> 1, b -> 2]|
# +----------------+df.collect()[0]['value']['a']
# 1

`StructField`

# 需要搭配 StructType 使用
StructField('column_name', DataType, is_nullable)

`StructType`

df = spark.createDataFrame([(1,)], schema=StructType([StructField('col', IntegerType())]))
df.show()
"""
+---+
|col|
+---+
|  1|
+---+
"""# 復雜一些的情況
df = spark.createDataFrame([({'a': [2,3,4]},)], schema=StructType([StructField('col', MapType(StringType(), ArrayType(IntegerType())))]))
df.show()
"""
+----------------+
|             col|
+----------------+
|[a -> [2, 3, 4]]|
+----------------+
"""df.collect()[0]['col']['a'][0]
# 2

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