如何在hadoop中使用python保存文件
如何在hadoop中使用python保存文件
提问于 2014-10-28 18:36:11
问题：
我开始学习hadoop，然而，我需要用python保存很多文件。我似乎找不出我做错了什么。有人能帮我吗？
下面是我的代码。我认为HDFS_PATH是正确的，因为我在安装时没有在设置中更改它。pythonfile.txt在我的桌面上(通过命令行运行的python代码也是如此)。
代码：
import hadoopy
import os
hdfs_path ='hdfs://localhost:9000/python'
def main():
hadoopy.writetb(hdfs_path, [('pythonfile.txt',open('pythonfile.txt').read())])
main()输出当我运行上面的代码时，我得到的只是python本身中的一个目录。
iMac-van-Brian:desktop Brian$ $HADOOP_HOME/bin/hadoop dfs -ls /python
DEPRECATED: Use of this script to execute hdfs command is deprecated.
Instead use the hdfs command for it.
14/10/28 11:30:05 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
-rw-r--r-- 1 Brian supergroup 236 2014-10-28 11:30 /python回答 3
Stack Overflow用户
发布于 2018-06-22 07:50:08
对于subprocess模块来说，这是一个非常典型的任务。解决方案看起来像这样：
put = Popen(["hadoop", "fs", "-put", <path/to/file>, <path/to/hdfs/file], stdin=PIPE, bufsize=-1)
put.communicate()完整示例
让我们假设你在一个服务器上，并且有一个经过验证的hdfs连接(例如，你已经调用了一个.keytab)。
您刚刚从pandas.DataFrame创建了一个csv，并希望将其放入hdfs。
然后，您可以将文件上传到hdfs，如下所示：
import os
import pandas as pd
from subprocess import PIPE, Popen
# define path to saved file
file_name = "saved_file.csv"
# create a pandas.DataFrame
sales = {'account': ['Jones LLC', 'Alpha Co', 'Blue Inc'], 'Jan': [150, 200, 50]}
df = pd.DataFrame.from_dict(sales)
# save your pandas.DataFrame to csv (this could be anything, not necessarily a pandas.DataFrame)
df.to_csv(file_name)
# create path to your username on hdfs
hdfs_path = os.path.join(os.sep, 'user', '<your-user-name>', file_name)
# put csv into hdfs
put = Popen(["hadoop", "fs", "-put", file_name, hdfs_path], stdin=PIPE, bufsize=-1)
put.communicate()csv文件将存在于/user/<your-user-name/saved_file.csv中。
注意-如果您从Hadoop中名为的python脚本创建此文件，则中间csv文件可能存储在一些随机节点上。由于(可能)不再需要此文件，因此最佳实践是删除它，以免每次调用脚本时都污染节点。您只需添加os.remove(file_name)作为上述脚本的最后一行即可解决此问题。
Stack Overflow用户
发布于 2014-10-28 22:16:17
我感觉您正在写入一个名为'/python‘的文件，而您打算将其作为存储该文件的目录
什么是
hdfs dfs -cat /python给你看？
如果它显示了文件内容，您所需要做的就是编辑您的hdfs_path以包含文件名(您应该首先使用-rm删除/python )，否则，使用pydoop (pip install pydoop)并执行以下操作：
import pydoop.hdfs as hdfs
from_path = '/tmp/infile.txt'
to_path ='hdfs://localhost:9000/python/outfile.txt'
hdfs.put(from_path, to_path)Stack Overflow用户
发布于 2018-01-17 22:04:56
我找到了这个答案here
import subprocess
def run_cmd(args_list):
"""
run linux commands
"""
# import subprocess
print('Running system command: {0}'.format(' '.join(args_list)))
proc = subprocess.Popen(args_list, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
s_output, s_err = proc.communicate()
s_return = proc.returncode
return s_return, s_output, s_err
#Run Hadoop ls command in Python
(ret, out, err)= run_cmd(['hdfs', 'dfs', '-ls', 'hdfs_file_path'])
lines = out.split('\n')
#Run Hadoop get command in Python
(ret, out, err)= run_cmd(['hdfs', 'dfs', '-get', 'hdfs_file_path', 'local_path'])
#Run Hadoop put command in Python
(ret, out, err)= run_cmd(['hdfs', 'dfs', '-put', 'local_file', 'hdfs_file_path'])
#Run Hadoop copyFromLocal command in Python
(ret, out, err)= run_cmd(['hdfs', 'dfs', '-copyFromLocal', 'local_file', 'hdfs_file_path'])
#Run Hadoop copyToLocal command in Python
(ret, out, err)= run_cmd(['hdfs', 'dfs', '-copyToLocal', 'hdfs_file_path', 'local_file'])
hdfs dfs -rm -skipTrash /path/to/file/you/want/to/remove/permanently
#Run Hadoop remove file command in Python
(ret, out, err)= run_cmd(['hdfs', 'dfs', '-rm', 'hdfs_file_path'])
(ret, out, err)= run_cmd(['hdfs', 'dfs', '-rm', '-skipTrash', 'hdfs_file_path'])
#rm -r
#HDFS Command to remove the entire directory and all of its content from #HDFS.
#Usage: hdfs dfs -rm -r <path>
(ret, out, err)= run_cmd(['hdfs', 'dfs', '-rm', '-r', 'hdfs_file_path'])
(ret, out, err)= run_cmd(['hdfs', 'dfs', '-rm', '-r', '-skipTrash', 'hdfs_file_path'])
#Check if a file exist in HDFS
#Usage: hadoop fs -test -[defsz] URI
#Options:
#-d: f the path is a directory, return 0.
#-e: if the path exists, return 0.
#-f: if the path is a file, return 0.
#-s: if the path is not empty, return 0.
#-z: if the file is zero length, return 0.
#Example:
#hadoop fs -test -e filename
hdfs_file_path = '/tmpo'
cmd = ['hdfs', 'dfs', '-test', '-e', hdfs_file_path]
ret, out, err = run_cmd(cmd)
print(ret, out, err)
if ret:
print('file does not exist')页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/26606128
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