代码之家 › 专栏 › 技术社区 › Markus

如何将字典列表转换为Spark数据帧

apache-spark-sql pyspark python

3

Markus · 技术社区 · 7 年前

我想把字典列表转换成数据帧。以下是列表:

mylist = 
[
  {"type_activity_id":1,"type_activity_name":"xxx"},
  {"type_activity_id":2,"type_activity_name":"yyy"},
  {"type_activity_id":3,"type_activity_name":"zzz"}
]

这是我的密码:

from pyspark.sql.types import StringType

df = spark.createDataFrame(mylist, StringType())

df.show(2,False)

+-----------------------------------------+
|                                    value|
+-----------------------------------------+
|{type_activity_id=1,type_activity_id=xxx}|
|{type_activity_id=2,type_activity_id=yyy}|
|{type_activity_id=3,type_activity_id=zzz}|
+-----------------------------------------+

我假设我应该为每一列提供一些映射和类型,但是我不知道怎么做。

我也试过这个:

schema = ArrayType(
    StructType([StructField("type_activity_id", IntegerType()),
                StructField("type_activity_name", StringType())
                ]))
df = spark.createDataFrame(mylist, StringType())
df = df.withColumn("value", from_json(df.value, schema))

但后来我 null 价值观:

+-----+
|value|
+-----+
| null|
| null|
+-----+

2 回复 | 直到 7 年前

1

8

Arvind 7 年前

你可以这样做。您将得到一个包含2列的数据帧。

mylist = [
  {"type_activity_id":1,"type_activity_name":"xxx"},
  {"type_activity_id":2,"type_activity_name":"yyy"},
  {"type_activity_id":3,"type_activity_name":"zzz"}
]

myJson = sc.parallelize(mylist)
myDf = sqlContext.read.json(myJson)

输出:

+----------------+------------------+
|type_activity_id|type_activity_name|
+----------------+------------------+
|               1|               xxx|
|               2|               yyy|
|               3|               zzz|
+----------------+------------------+

2

22

pault Tanjin 7 年前

spark.createDataFrame() ,但现在不赞成这样做:

mylist = [
  {"type_activity_id":1,"type_activity_name":"xxx"},
  {"type_activity_id":2,"type_activity_name":"yyy"},
  {"type_activity_id":3,"type_activity_name":"zzz"}
]
df = spark.createDataFrame(mylist)
#UserWarning: inferring schema from dict is deprecated,please use pyspark.sql.Row instead
#  warnings.warn("inferring schema from dict is deprecated,"

正如警告信息所说,您应该使用 pyspark.sql.Row

from pyspark.sql import Row
spark.createDataFrame(Row(**x) for x in mylist).show(truncate=False)
#+----------------+------------------+
#|type_activity_id|type_activity_name|
#+----------------+------------------+
#|1               |xxx               |
#|2               |yyy               |
#|3               |zzz               |
#+----------------+------------------+

我用过这里 ** keyword argument unpacking )把字典传给 Row 建造师。

3

1

anvy elizabeth 6 年前

在Spark版本2.4中,可以直接使用测向=spark.createDataFrame(我的列表)

>>> mylist = [
...   {"type_activity_id":1,"type_activity_name":"xxx"},
...   {"type_activity_id":2,"type_activity_name":"yyy"},
...   {"type_activity_id":3,"type_activity_name":"zzz"}
... ]
>>> df1=spark.createDataFrame(mylist)
>>> df1.show()
+----------------+------------------+
|type_activity_id|type_activity_name|
+----------------+------------------+
|               1|               xxx|
|               2|               yyy|
|               3|               zzz|
+----------------+------------------+

4

0

Athar 6 年前

我在创作时也面临着同样的问题 dataframe 从字典列表中。我已经解决了这个问题 namedtuple .

下面是我的代码使用提供的数据。

from collections import namedtuple
final_list = []
mylist = [{"type_activity_id":1,"type_activity_name":"xxx"},
          {"type_activity_id":2,"type_activity_name":"yyy"}, 
          {"type_activity_id":3,"type_activity_name":"zzz"}
         ]
ExampleTuple = namedtuple('ExampleTuple', ['type_activity_id', 'type_activity_name'])

for my_dict in mylist:
    namedtupleobj = ExampleTuple(**my_dict)
    final_list.append(namedtupleobj)

sqlContext.createDataFrame(final_list).show(truncate=False)

输出

+----------------+------------------+
|type_activity_id|type_activity_name|
+----------------+------------------+
|1               |xxx               |
|2               |yyy               |
|3               |zzz               |
+----------------+------------------+

spark: 2.4.0
python: 3.6

没有必要有 my_list 变量。因为它是可用的,所以我用它直接创建namedtuple对象可以创建对象。