【Python学习笔记】4. Python大数据编程入门

4.1 Python操作MySQL

​ 首先需要安装pymysql外部包

from pymysql import Connection

# 构建到MySQL数据库的连接
connection = Connection(
	host="localhost",
	port=3306,
	user="root",
	password="123456"
)

# 获取游标
cunsor = connection.cursor()
# 选择数据库
connection.select_db("test")
# 执行sql
cunsor.execute("select * from people")
# 获取查询结果
results : tuple = cunsor.fetchall()
for result in results:
	print(result)
# 关闭连接
connection.close()

​ 在插入数据时，需要手动提交事务

connection.commit()

​ 或者在Connection构造方法中传参

autocommit=True

4.2 Spark与PySpark

4.2.1 PySpark基础

• Spark是Apache基金会旗下的顶级开源项目，用于对海量数据进行大规模分布式计算。

• PySpark是Spark的Python实现，是Spark为Python开发者提供的编程入口，用于以Python代码完成Spark任务的开发

• PySpark不仅可以作为Python第三方库使用，也可以将程序提交的Spark集群环境中，调度大规模集群进行执行。

• 国内代理镜像网站（清华大学源）
  pip install -i https://pypi.tuna.tsinghua.edu.cn/simple pyspark

• PySpark的编程，主要分为三个步骤

  

想要使用PySpark库完成数据处理，首先需要构建一个执行环境入口对象。

PySpark的执行环境入口对象是：类 SparkContext 的类对象

SparkContext类对象，是PySpark编程中一切功能的入口。

from pyspark import SparkConf, SparkContext

# 创建SparkConf对象
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")

# 基于SparkConf对象创建SparkContext对象
sc = SparkContext(conf=conf)

# 打印PySpark的运行版本
print(sc.version)

# 停止SparkContext运行（停止PySpark程序）
sc.stop()

4.2.2 数据输入

• PySpark支持多种数据的输入，在输入完成后，都会得到一个：RDD类的对象

• RDD全称为：弹性分布式数据集（Resilient Distributed Datasets）

• RDD对象称之为分布式弹性数据集，是PySpark中数据计算的载体，它可以：

  • 提供数据存储
  • 提供数据计算的各类方法
  • 数据计算的方法，返回值依旧是RDD（RDD迭代计算）

4.2.2.1 Python数据容器转换为RDD对象

from pyspark import SparkConf, SparkContext

# 创建SparkConf对象和SparkContext对象
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
sc = SparkContext(conf=conf)

# 通过SparkContext的parallelize成员方法，将Python数据容器转换为RDD对象
rdd1 = sc.parallelize([1, 2, 3, 4, 5])
rdd2 = sc.parallelize((1, 2, 3, 4, 5))
rdd3 = sc.parallelize("abcdefg")
rdd4 = sc.parallelize({1, 2, 3, 4, 5})
rdd5 = sc.parallelize({"key1": "value1", "key2": "value2"})

# 如果要查看RDD中的内容，需要调用collect()方法
print(rdd1.collect())
print(rdd2.collect())
print(rdd3.collect())
print(rdd4.collect())
print(rdd5.collect())

# 停止SparkContext运行（停止PySpark程序）
sc.stop()

4.2.2.2 读取文本文件得到RDD对象

from pyspark import SparkConf, SparkContext

# 创建SparkConf对象和SparkContext对象
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
sc = SparkContext(conf=conf)

# 通过SparkContext的textFile成员方法，读取文本文件得到RDD对象
rdd = sc.textFile("D:\\MyStudy\\MyCode\\PycharmProjects\\py_mysql\\test.txt")
print(rdd.collect())

# 停止SparkContext运行（停止PySpark程序）
sc.stop()

4.2.3 数据计算

4.2.3.1 map算子

• map算子是将RDD的数据一条条处理（处理的逻辑基于map算子中接收的处理函数），返回新的RDD

from pyspark import SparkConf, SparkContext
import os
os.environ['PYSPARK_PYTHON'] = "D:\\MyStudy\\Environment\\Python\\Python310\\python.exe"

# 创建SparkConf对象和SparkContext对象
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
sc = SparkContext(conf=conf)

# 准备一个RDD
rdd = sc.parallelize([1, 2, 3, 4, 5])

# 通过map方法将全部数据都乘以十，链式调用
rdd2 = rdd.map(lambda data: data * 10).map(lambda data: data + 5)
print(rdd2.collect())

# 停止SparkContext运行（停止PySpark程序）
sc.stop()

4.2.3.2 flatMap算子

• 对rdd执行map操作，然后进行解除嵌套操作。

from pyspark import SparkConf, SparkContext
import os
os.environ['PYSPARK_PYTHON'] = "D:\\MyStudy\\Environment\\Python\\Python310\\python.exe"

# 创建SparkConf对象和SparkContext对象
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
sc = SparkContext(conf=conf)

# 准备一个RDD
rdd = sc.parallelize(["this is", "python 310", "flatmap", "rdd spark"])

# 通过map方法将全部数据都乘以十，链式调用
rdd2 = rdd.flatMap(lambda data: data.split(" "))
print(rdd2.collect())

# 停止SparkContext运行（停止PySpark程序）
sc.stop()

4.2.3.3 reduceByKey算子

• 针对KV型RDD，自动按照key分组**，然后根据你提供的聚合逻辑，完成组内数据（value）的聚合操作。

from pyspark import SparkConf, SparkContext
import os

os.environ['PYSPARK_PYTHON'] = "D:\\MyStudy\\Environment\\Python\\Python310\\python.exe"
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
sc = SparkContext(conf=conf)

# 准备一个RDD
rdd = sc.parallelize([('boy', 99), ('boy', 88), ('boy', 77), ('girl', 99), ('girl', 66)])
# 求男生和女生两个组的成绩之和
rdd2 = rdd.reduceByKey(lambda a, b: a + b)
print(rdd2.collect())

sc.stop()

4.2.3.4 案例：单词计数

提前设置好一个等待读取的txt文档：

spark python java zhang rdd python rdd
python java cpp c cpp spark pyspark zhang
rdd c python py pyspark python pp rdd

from pyspark import SparkConf, SparkContext
import os

os.environ['PYSPARK_PYTHON'] = "D:\\MyStudy\\Environment\\Python\\Python310\\python.exe"
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
sc = SparkContext(conf=conf)

# 读取数据文件
rdd = sc.textFile("D:\\MyStudy\\MyCode\\PycharmProjects\\py_mysql\\test.txt")

# 取出全部单词
word_rdd = rdd.flatMap(lambda data: data.split(" "))

# 将单词转换为二元元组，单词为key，value设置为1
word_one_rdd = word_rdd.map(lambda word: (word, 1))

# 分组求和
result_rdd = word_one_rdd.reduceByKey(lambda a, b: a + b)

# 打印结果
print(result_rdd.collect())

sc.stop()

4.2.3.5 filter算子

• 接受一个处理函数，可用lambda快速编写

• 函数对RDD数据逐个处理，得到True的保留至返回值的RDD中

from pyspark import SparkConf, SparkContext
import os

os.environ['PYSPARK_PYTHON'] = "D:\\MyStudy\\Environment\\Python\\Python310\\python.exe"
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
sc = SparkContext(conf=conf)

# 取出列表中的奇数
rdd = sc.parallelize([1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
rdd2 = rdd.filter(lambda num: num % 2 == 0)

print(rdd2.collect())

sc.stop()

4.2.3.6 distinct算子

• 去重，返回新RDD对象

from pyspark import SparkConf, SparkContext
import os

os.environ['PYSPARK_PYTHON'] = "D:\\MyStudy\\Environment\\Python\\Python310\\python.exe"
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
sc = SparkContext(conf=conf)

rdd = sc.parallelize([1, 2, 3, 4, 5, 1, 2, 6, 7, 3])
rdd2 = rdd.distinct()

print(rdd2.collect())

sc.stop()

4.2.3.7 sortBy算子

• 对RDD数据进行排序，基于指定的排序依据
• 对单词统计案例中的结果进行排序

from pyspark import SparkConf, SparkContext
import os

os.environ['PYSPARK_PYTHON'] = "D:\\MyStudy\\Environment\\Python\\Python310\\python.exe"
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
sc = SparkContext(conf=conf)

rdd = sc.textFile("D:\\MyStudy\\MyCode\\PycharmProjects\\py_mysql\\test.txt")
word_rdd = rdd.flatMap(lambda data: data.split(" "))
word_one_rdd = word_rdd.map(lambda word: (word, 1))
result_rdd = word_one_rdd.reduceByKey(lambda a, b: a + b)

result_rdd_sortBy = result_rdd.sortBy(lambda t: t[1], ascending=False, numPartitions=1)

print(result_rdd_sortBy.collect())

sc.stop()

4.2.3.8 案例：货物售卖统计

需求：把下述内容写入txt文件，使用Spark读取文件进行计算

• 各个城市销售额排名，从大到小

• 全部城市，有哪些商品类别在售卖

• 北京市有哪些商品类别在售卖

{"id":1,"timestamp":"2019-05-08T01:03.00Z","category":"平板电脑","areaName":"北京","money":"1450"}|{"id":2,"timestamp":"2019-05-08T01:01.00Z","category":"手机","areaName":"北京","money":"1450"}|{"id":3,"timestamp":"2019-05-08T01:03.00Z","category":"手机","areaName":"北京","money":"8412"}
{"id":4,"timestamp":"2019-05-08T05:01.00Z","category":"电脑","areaName":"上海","money":"1513"}|{"id":5,"timestamp":"2019-05-08T01:03.00Z","category":"家电","areaName":"北京","money":"1550"}|{"id":6,"timestamp":"2019-05-08T01:01.00Z","category":"电脑","areaName":"杭州","money":"1550"}
{"id":7,"timestamp":"2019-05-08T01:03.00Z","category":"电脑","areaName":"北京","money":"5611"}|{"id":8,"timestamp":"2019-05-08T03:01.00Z","category":"家电","areaName":"北京","money":"4410"}|{"id":9,"timestamp":"2019-05-08T01:03.00Z","category":"家具","areaName":"郑州","money":"1120"}
{"id":10,"timestamp":"2019-05-08T01:01.00Z","category":"家具","areaName":"北京","money":"6661"}|{"id":11,"timestamp":"2019-05-08T05:03.00Z","category":"家具","areaName":"杭州","money":"1230"}|{"id":12,"timestamp":"2019-05-08T01:01.00Z","category":"书籍","areaName":"北京","money":"5550"}
{"id":13,"timestamp":"2019-05-08T01:03.00Z","category":"书籍","areaName":"北京","money":"5550"}|{"id":14,"timestamp":"2019-05-08T01:01.00Z","category":"电脑","areaName":"北京","money":"1261"}|{"id":15,"timestamp":"2019-05-08T03:03.00Z","category":"电脑","areaName":"杭州","money":"6660"}
{"id":16,"timestamp":"2019-05-08T01:01.00Z","category":"电脑","areaName":"天津","money":"6660"}|{"id":17,"timestamp":"2019-05-08T01:03.00Z","category":"书籍","areaName":"北京","money":"9000"}|{"id":18,"timestamp":"2019-05-08T05:01.00Z","category":"书籍","areaName":"北京","money":"1230"}
{"id":19,"timestamp":"2019-05-08T01:03.00Z","category":"电脑","areaName":"杭州","money":"5551"}|{"id":20,"timestamp":"2019-05-08T01:01.00Z","category":"电脑","areaName":"北京","money":"2450"}
{"id":21,"timestamp":"2019-05-08T01:03.00Z","category":"食品","areaName":"北京","money":"5520"}|{"id":22,"timestamp":"2019-05-08T01:01.00Z","category":"食品","areaName":"北京","money":"6650"}
{"id":23,"timestamp":"2019-05-08T01:03.00Z","category":"服饰","areaName":"杭州","money":"1240"}|{"id":24,"timestamp":"2019-05-08T01:01.00Z","category":"食品","areaName":"天津","money":"5600"}
{"id":25,"timestamp":"2019-05-08T01:03.00Z","category":"食品","areaName":"北京","money":"7801"}|{"id":26,"timestamp":"2019-05-08T01:01.00Z","category":"服饰","areaName":"北京","money":"9000"}
{"id":27,"timestamp":"2019-05-08T01:03.00Z","category":"服饰","areaName":"杭州","money":"5600"}|{"id":28,"timestamp":"2019-05-08T01:01.00Z","category":"食品","areaName":"北京","money":"8000"}|{"id":29,"timestamp":"2019-05-08T02:03.00Z","category":"服饰","areaName":"杭州","money":"7000"}

from pyspark import SparkConf, SparkContext
import os
import json

os.environ['PYSPARK_PYTHON'] = "D:\\MyStudy\\Environment\\Python\\Python310\\python.exe"
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
sc = SparkContext(conf=conf)

# 公共操作
# 打开文件并获取每个json字符串
file_rdd = sc.textFile("D:\\MyStudy\\MyCode\\PycharmProjects\\py_mysql\\data.txt")
json_str_rdd = file_rdd.flatMap(lambda data: data.split("|"))
# 通过json类的类方法转化为字典对象
dict_rdd = json_str_rdd.map(lambda data: json.loads(data))


# TODO 需求1：城市销售额排名
# 清洗数据，保留字典中的有用信息
clear_data_rdd = dict_rdd.map(lambda data: (data['areaName'], int(data['money'])))
# 按照地名，聚合数据，并进行排序
aggregation_rdd = clear_data_rdd.reduceByKey(lambda a, b: a + b)
aggregation_sort_rdd = aggregation_rdd.sortBy(lambda x: x[1], ascending=False, numPartitions=1)
# 打印结果
print(f"城市销售额排名为：{aggregation_sort_rdd.collect()}")


# TODO 需求2：全部城市中有哪些商品在售卖
# 清洗数据，保留字典中的有用信息
clear_data_rdd = dict_rdd.map(lambda data: (data['category']))
# 去重
category_rdd = clear_data_rdd.distinct()
# 打印结果
print(f"所有正在售卖的商品有：{category_rdd.collect()}")


# TODO 需求3：北京有哪些商品在售卖
# 过滤数据，保留满足地名为北京的json数据
bj_rdd = dict_rdd.filter(lambda data: data['areaName'] == '北京')
# 清洗数据，保留字典中的有用信息
clear_data_rdd = bj_rdd.map(lambda data: (data['category']))
# 去重
category_rdd = clear_data_rdd.distinct()
# 打印结果
print(f"北京正在售卖的商品有：{category_rdd.collect()}")

# 公共操作
sc.stop()

4.2.4 数据输出

• collect：将RDD内容转换为list

• reduce：对RDD内容进行自定义聚合

• take：取出RDD的前N个元素组成list

• count：统计RDD元素个数

4.2.4.1 collect算子

• 将RDD各个分区内的数据，统一收集到Driver中，形成一个List对象

from pyspark import SparkConf, SparkContext
import os

os.environ['PYSPARK_PYTHON'] = "D:\\MyStudy\\Environment\\Python\\Python310\\python.exe"
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
sc = SparkContext(conf=conf)

rdd = sc.parallelize([1, 2, 3, 4, 5])
print(rdd.collect())
print(type(rdd.collect()))

sc.stop()

4.2.4.2 reduce算子

• 对RDD数据集按照你传入的逻辑进行聚合

from pyspark import SparkConf, SparkContext
import os

os.environ['PYSPARK_PYTHON'] = "D:\\MyStudy\\Environment\\Python\\Python310\\python.exe"
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
sc = SparkContext(conf=conf)

rdd = sc.parallelize([1, 2, 3, 4, 5])
num = rdd.reduce(lambda a, b: a + b)
print(num)

sc.stop()

4.2.4.3 take算子

• 取RDD的前N个元素，组合成list返回

from pyspark import SparkConf, SparkContext
import os

os.environ['PYSPARK_PYTHON'] = "D:\\MyStudy\\Environment\\Python\\Python310\\python.exe"
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
sc = SparkContext(conf=conf)

rdd = sc.parallelize([1, 2, 3, 4, 5])
rdd2 = rdd.take(3)
print(rdd2)

sc.stop()

4.2.4.4 count算子

• 计算RDD有多少条数据，返回值是一个数字

from pyspark import SparkConf, SparkContext
import os

os.environ['PYSPARK_PYTHON'] = "D:\\MyStudy\\Environment\\Python\\Python310\\python.exe"
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
sc = SparkContext(conf=conf)

rdd = sc.parallelize([1, 2, 3, 4, 5])
rdd2 = rdd.count()
print(rdd2)

sc.stop()

4.2.4.5 输出到文件（saveAsTextFile算子）

• 将RDD的数据写入文本文件中

• 支持本地写出，hdfs等文件系统

• 调用保存文件的算子，需要配置Hadoop依赖

  • 下载Hadoop安装包

    • http://archive.apache.org/dist/hadoop/common/hadoop-3.0.0/hadoop-3.0.0.tar.gz

  • 解压到电脑任意位置

  • 在Python代码中使用os模块配置：os.environ[‘HADOOP_HOME’] = ‘HADOOP解压文件夹路径’

  • 下载winutils.exe，并放入Hadoop解压文件夹的bin目录内

    • https://raw.githubusercontent.com/steveloughran/winutils/master/hadoop-3.0.0/bin/winutils.exe

  • 下载hadoop.dll，并放入:C:/Windows/System32 文件夹内

    • https://raw.githubusercontent.com/steveloughran/winutils/master/hadoop-3.0.0/bin/hadoop.dll

• 修改rdd分区为1个

  • case1：SparkConf对象设置属性全局并行度为1：

    conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
    conf.set("spark.default.parallelism", "1")
    sc = SparkContext(conf=conf)
    

  • case2：创建RDD的时候设置（parallelize方法传入numSlices参数为1）

    rdd1 = sc.parallelize([1, 2, 3, 4, 5], numSlices=1)
    # 或者
    rdd2 = sc.parallelize([1, 2, 3, 4, 5], 1)
    
    rdd1.saveAsTextFile("rdd1")
    rdd2.saveAsTextFile("rdd2")
    

4.2.5 案例：搜索引擎日志分析

• 读取文件转换成RDD，并完成：
  • 打印输出：热门搜索时间段（小时精度）Top3
  • 打印输出：热门搜索词Top3
  • 打印输出：统计黑马程序员关键字在哪个时段被搜索最多
  • 将数据转换为JSON格式，写出为文件

from pyspark import SparkConf, SparkContext
import os

os.environ['PYSPARK_PYTHON'] = "D:\\MyStudy\\Environment\\Python\\Python310\\python.exe"
os.environ['HADOOP_HOME'] = "D:\\MyStudy\\Environment\\Hadoop\\spark-3.3.1-bin-hadoop3"
conf = SparkConf().setMaster("local[*]").setAppName("test_spark_app")
conf.set("spark.default.parallelism", "1")
sc = SparkContext(conf=conf)

# 读取文件转化为RDD
file_rdd = sc.textFile("D:\\MyStudy\\MyCode\\PycharmProjects\\py_mysql\\search_log.txt")

# TODO 需求1：热门搜索时间段（小时精度）Top3
# 将rdd返回的list中的每个元素按\t划分，列表嵌套
# 每行（内层列表）第0个元素即为时间，如：00:00:00，且前两位为小时
# 将小时组装为元组，并按照小时进行聚合
# 按照出现总次数进行降序排序，取前三位即为TOP3
result1 = file_rdd.map(lambda x: x.split("\t")). \
	map(lambda x: x[0][:2]). \
	map(lambda x: (x + "点", 1)). \
	reduceByKey(lambda a, b: a + b). \
	sortBy(lambda x: x[1], ascending=False, numPartitions=1). \
	take(3)

print(f"热门搜索时间段（小时精度）Top3：{result1}")

# TODO 需求2：热门搜索词Top3
result2 = file_rdd.map(lambda x: (x.split("\t")[2], 1)). \
	reduceByKey(lambda a, b: a + b). \
	sortBy(lambda x: x[1], ascending=False, numPartitions=1). \
	take(3)

print(f"热门搜索词Top3：{result2}")

# TODO 需求3：统计黑马程序员关键字在哪个时段被搜索最多
result3 = file_rdd.map(lambda x: x.split("\t")). \
	filter(lambda x: x[2] == "黑马程序员"). \
	map(lambda x: (x[0][:2], 1)). \
	reduceByKey(lambda a, b: a + b). \
	sortBy(lambda x: x[1], ascending=False, numPartitions=1). \
	take(1)

print(f"统计黑马程序员关键字在哪个时段被搜索最多：{result3}")

# TODO 需求4：将数据转换为JSON格式，写出为文件
file_rdd.map(lambda x: x.split("\t")). \
	map(lambda x: {"time": x[0], "user_id": x[1], "key_word": x[2], "rank1": x[3], "rank2": x[4], "url": x[5]}). \
	saveAsTextFile("output_json")

print("文件已写出")

sc.stop()