spark 常見問題pyspark Cannot run multiple SparkContexts at once; existing SparkContext

在是使用 pyspark 連接spark 時出現一下錯誤，當時試了很多方都沒有解決，最後終於解決。如下所示

from pyspark import SparkContext

from pyspark import SparkConf
import pyspark

string_test = 'pyspark_test'
print(pyspark.__version__)

conf = SparkConf().setAppName(string_test).setMaster('spark://master:7077')

sc = SparkContext(conf=conf)
#
list_test = [1, 2, 3]

x = sc.parallelize(list_test)

y = x.map(lambda x: (x, x * 2))

print (x.collect())

print (y.collect())

sc.stop()

報錯

ValueError: Cannot run multiple SparkContexts at once; existing SparkContext(app=PySparkShell, master=local[*]) created by <module> at /usr/local/spark/python/pyspark/shell.py:59 

解決辦法
出現這個錯誤是因爲之前已將啓動了SparkContext ,所以需要先關閉spark，然後再啓動