快上网专注成都网站设计 成都网站制作 成都网站建设
成都网站建设公司服务热线：028-86922220

网站建设知识

十年网站开发经验 + 多家企业客户 + 靠谱的建站团队

量身定制 + 运营维护+专业推广+无忧售后，网站问题一站解决

SparkPython操作命令三

12 数据格式

10年积累的成都网站设计、网站建设经验，可以快速应对客户对网站的新想法和需求。提供各种问题对应的解决方案。让选择我们的客户得到更好、更有力的网络服务。我虽然不认识你，你也不认识我。但先网站制作后付款的网站建设流程，更有沾化免费网站建设让你可以放心的选择与我们合作。

  1. [[u'3', u'5'], [u'4', u'6'], [u'4', u'5'], [u'4', u'2']] 拆分或截取的原始数据， 可以通过 map 中的 x[0], x[1] 来获取对应列的数据
    可以通过 map 来转换为key-value 数据格式 例如： df3 = df2.map(lambda x: (x[0], x[1]))

  2. key-value 数据格式
    [(u'3', u'5'), (u'4', u'6'), (u'4', u'5'), (u'4', u'2')] 中每一个（） 表示一组数据， 第一个表示key 第二个表示value
    3）PipelinedRDD 类型表示 key-value形式数据
    13 RDD类型转换
    userRdd = sc.textFile("D:\data\people.json")
    userRdd = userRdd.map(lambda x: x.split(" "))

    userRows = userRdd.map(lambda p:
                        Row(
                            userName = p[0],
                            userAge = int(p[1]),
                            userAdd = p[2],
                            userSalary = int(p[3])
                            )
                        )
print(userRows.take(4))

    结果： [Row(userAdd='shanghai', userAge=20, userName='zhangsan', userSalary=13), Row(userAdd='beijin', userAge=30, userName='lisi', userSalary=15)]

    2） 创建 DataFrame
    userDF = sqlContext.createDataFrame(userRows)

    1. 通过sql 语句查询字段
      from pyspark.conf import SparkConf
      from pyspark.sql.session import SparkSession
      from pyspark.sql.types import Row

if name== 'main':
spark = SparkSession.builder.config(conf = SparkConf()).getOrCreate()

sc = spark.sparkContext

rd = sc.textFile("D:\data\people.txt")
rd2 = rd.map(lambda x:x.split(","))
people = rd2.map(lambda p: Row(name=p[0], age=int(p[1])))

peopleDF = spark.createDataFrame(people)
peopleDF.createOrReplaceTempView("people")
teenagers = spark.sql("SELECT name,age FROM people where name='Andy'")
teenagers.show(5)

print(teenagers.rdd.collect())

teenNames = teenagers.rdd.map(lambda p: 100 + p.age).collect()

for name in teenNames:
    print(name)

15 dateFrame,sql,json使用详细示例
#

Licensed to the Apache Software Foundation (ASF) under one or more

contributor license agreements. See the NOTICE file distributed with

this work for additional information regarding copyright ownership.

The ASF licenses this file to You under the Apache License, Version 2.0

(the "License"); you may not use this file except in compliance with

the License. You may obtain a copy of the License at

#

http://www.apache.org/licenses/LICENSE-2.0

#

Unless required by applicable law or agreed to in writing, software

distributed under the License is distributed on an "AS IS" BASIS,

WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

See the License for the specific language governing permissions and

limitations under the License.

#

"""
A simple example demonstrating basic Spark SQL features.
Run with:
./bin/spark-submit examples/src/main/python/sql/basic.py
"""
from futureimport print_function

$example on:init_session$

from pyspark.sql import SparkSession

$example off:init_session$

$example on:schema_inferring$

from pyspark.sql import Row

$example off:schema_inferring$

$example on:programmatic_schema$

Import data types

from pyspark.sql.types import *

$example off:programmatic_schema$

def basic_df_example(spark):

$example on:create_df$

# spark is an existing SparkSession
df = spark.read.json("/data/people.json")
# Displays the content of the DataFrame to stdout
df.show()
# +----+-------+
# | age|   name|
# +----+-------+
# |null|Michael|
# |  30|   Andy|
# |  19| Justin|
# +----+-------+
# $example off:create_df$

# $example on:untyped_ops$
# spark, df are from the previous example
# Print the schema in a tree format
df.printSchema()
# root
# |-- age: long (nullable = true)
# |-- name: string (nullable = true)

# Select only the "name" column
df.select("name").show()
# +-------+
# |   name|
# +-------+
# |Michael|
# |   Andy|
# | Justin|
# +-------+

# Select everybody, but increment the age by 1
df.select(df['name'], df['age'] + 1).show()
# +-------+---------+
# |   name|(age + 1)|
# +-------+---------+
# |Michael|     null|
# |   Andy|       31|
# | Justin|       20|
# +-------+---------+

# Select people older than 21
df.filter(df['age'] > 21).show()
# +---+----+
# |age|name|
# +---+----+
# | 30|Andy|
# +---+----+

# Count people by age
df.groupBy("age").count().show()
# +----+-----+
# | age|count|
# +----+-----+
# |  19|    1|
# |null|    1|
# |  30|    1|
# +----+-----+
# $example off:untyped_ops$

# $example on:run_sql$
# Register the DataFrame as a SQL temporary view
df.createOrReplaceTempView("people")

sqlDF = spark.sql("SELECT * FROM people")
sqlDF.show()
# +----+-------+
# | age|   name|
# +----+-------+
# |null|Michael|
# |  30|   Andy|
# |  19| Justin|
# +----+-------+
# $example off:run_sql$

# $example on:global_temp_view$
# Register the DataFrame as a global temporary view
df.createGlobalTempView("people")

# Global temporary view is tied to a system preserved database `global_temp`
spark.sql("SELECT * FROM global_temp.people").show()
# +----+-------+
# | age|   name|
# +----+-------+
# |null|Michael|
# |  30|   Andy|
# |  19| Justin|
# +----+-------+

# Global temporary view is cross-session
spark.newSession().sql("SELECT * FROM global_temp.people").show()
# +----+-------+
# | age|   name|
# +----+-------+
# |null|Michael|
# |  30|   Andy|
# |  19| Justin|
# +----+-------+
# $example off:global_temp_view$

def schema_inference_example(spark):

$example on:schema_inferring$

sc = spark.sparkContext

# Load a text file and convert each line to a Row.
lines = sc.textFile("examples/src/main/resources/people.txt")
parts = lines.map(lambda l: l.split(","))
people = parts.map(lambda p: Row(name=p[0], age=int(p[1])))

# Infer the schema, and register the DataFrame as a table.
schemaPeople = spark.createDataFrame(people)
schemaPeople.createOrReplaceTempView("people")

# SQL can be run over DataFrames that have been registered as a table.
teenagers = spark.sql("SELECT name FROM people WHERE age >= 13 AND age <= 19")

# The results of SQL queries are Dataframe objects.
# rdd returns the content as an :class:`pyspark.RDD` of :class:`Row`.
teenNames = teenagers.rdd.map(lambda p: "Name: " + p.name).collect()
for name in teenNames:
    print(name)
# Name: Justin
# $example off:schema_inferring$

def programmatic_schema_example(spark):

$example on:programmatic_schema$

sc = spark.sparkContext

# Load a text file and convert each line to a Row.
lines = sc.textFile("examples/src/main/resources/people.txt")
parts = lines.map(lambda l: l.split(","))
# Each line is converted to a tuple.
people = parts.map(lambda p: (p[0], p[1].strip()))

# The schema is encoded in a string.
schemaString = "name age"

fields = [StructField(field_name, StringType(), True) for field_name in schemaString.split()]
schema = StructType(fields)

# Apply the schema to the RDD.
schemaPeople = spark.createDataFrame(people, schema)

# Creates a temporary view using the DataFrame
schemaPeople.createOrReplaceTempView("people")

# SQL can be run over DataFrames that have been registered as a table.
results = spark.sql("SELECT name FROM people")

results.show()
# +-------+
# |   name|
# +-------+
# |Michael|
# |   Andy|
# | Justin|
# +-------+
# $example off:programmatic_schema$

if name== "main":

$example on:init_session$

spark = SparkSession \
    .builder \
    .appName("Python Spark SQL basic example") \
    .config("spark.some.config.option", "some-value") \
    .getOrCreate()
# $example off:init_session$

basic_df_example(spark)
# schema_inference_example(spark)
# programmatic_schema_example(spark)

spark.stop()

文章标题：SparkPython操作命令三
新闻来源：http://6mz.cn/article/ipsjes.html

其他资讯