hdfs基本操作-python接口

HDFS操作手册

hdfscli命令行

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# hdfscli --help

HdfsCLI: a command line interface for HDFS.

Usage:

hdfscli [interactive] [-a ALIAS] [-v...]

hdfscli download [-fsa ALIAS] [-v...] [-t THREADS] HDFS_PATH LOCAL_PATH

hdfscli upload [-sa ALIAS] [-v...] [-A | -f] [-t THREADS] LOCAL_PATH HDFS_PATH

hdfscli -L | -V | -h

Commands:

download Download a file or folder from HDFS. If a

single file is downloaded, - can be

specified as LOCAL_PATH to stream it to

standard out.

interactive Start the client and expose it via the python

interpreter (using iPython if available).

upload Upload a file or folder to HDFS. - can be

specified as LOCAL_PATH to read from standard

in.

Arguments:

HDFS_PATH Remote HDFS path.

LOCAL_PATH Path to local file or directory.

Options:

-A --append Append data to an existing file. Only supported

if uploading a single file or from standard in.

-L --log Show path to current log file and exit.

-V --version Show version and exit.

-a ALIAS --alias=ALIAS Alias of namenode to connect to.

-f --force Allow overwriting any existing files.

-s --silent Don't display progress status.

-t THREADS --threads=THREADS Number of threads to use for parallelization.

0 allocates a thread per file. [default: 0]

-v --verbose Enable log output. Can be specified up to three

times (increasing verbosity each time).

Examples:

hdfscli -a prod /user/foo

hdfscli download features.avro dat/

hdfscli download logs/1987-03-23 - >>logs

hdfscli upload -f - data/weights.tsv <weights.tsv

HdfsCLI exits with return status 1 if an error occurred and 0 otherwise.

要使用hdfscli，首先需要设置hdfscli的默认配置文件

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# cat ~/.hdfscli.cfg

[global]

default.alias = dev

[dev.alias]

url = http://hadoop:50070

user = root

　　蟒蛇可用的客户端类：

　　　　InsecureClient（默认）

　　　　TokenClient

上传或下载文件

使用hdfscli上传文件或文件夹（将hadoop的文件夹上传到/ HDFS）

　　#hdfscli upload --alias = dev -f /hadoop-2.4.1/etc/hadoop/ / hdfs

使用hdfscli下载/日志目录到操作系统的/根/测试目录下

　　#hdfscli下载/ logs / root / test /

hdfscli交互模式

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[root@hadoop ~]# hdfscli --alias=dev

Welcome to the interactive HDFS python shell.

The HDFS client is available as `CLIENT`.

>>> CLIENT.list("/")

[u'Demo', u'hdfs', u'logs', u'logss']

>>> CLIENT.status("/Demo")

{u'group': u'supergroup', u'permission': u'755', u'blockSize': 0,

u'accessTime': 0, u'pathSuffix': u'', u'modificationTime': 1495123035501L,

u'replication': 0, u'length': 0, u'childrenNum': 1, u'owner': u'root',

u'type': u'DIRECTORY', u'fileId': 16389}

>>> CLIENT.delete("logs/install.log")

False

>>> CLIENT.delete("/logs/install.log")

True

与python接口的绑定

　　初始化客户端

　　1，导入客户端类，然后调用它的构造函数

>>> from hdfs import InsecureClient

>>> client = InsecureClient("http://172.10.236.21:50070",user='ann')

>>> client.list("/")

[u'Demo', u'hdfs', u'logs', u'logss']

　　2，导入配置类，加载一个已存在的配置文件并且从已存在的别名创建一个客户端，配置文件默认的读取文件为〜/ .hdfs_config.cfg

>>> from hdfs import Config

>>> client=Config().get_client("dev")

>>> client.list("/")

[u'Demo', u'hdfs', u'logs', u'logss']

　　读文件

　　读（）方法可从HDFS系统读取一个文件，但是它必须放在与块中，以确保每次都能正确关闭连接

>>> with client.read("/logs/yarn-env.sh"，encoding="utf-8") as reader:

... features=reader.read()

...

>>> print features

　　CHUNK_SIZE参数将返回一个生成器，它使文件的内容变成流数据

>>> with client.read("/logs/yarn-env.sh",chunk_size=1024) as reader:

... for chunk in reader:

... print chunk

...

　　分隔符参数同样返回一个生成器，文件内容是被指定符号分隔的

>>> with client.read("/logs/yarn-env.sh", encoding="utf-8", delimiter="\n") as reader:

... for line in reader:

... time.sleep(1)

... print line

　　写文件

写方法用于写文件到HDFS（将本地文件kong.txt写入HDFS的/logs/kongtest.txt文件中）

>>> with open("/root/test/kong.txt") as reader, client.write("/logs/kongtest.txt") as writer:

... for line in reader:

... if line.startswith("-"):

... writer.write(line)

原文见：HTTP：//www.cnblogs.com/kongzhagen/p/6877472.html

HDFS基本操作-python接口

安装HDFS包

　　点安装HDFS：可以通过命令pip install hdfs进行安装。

查看HDFS目录

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[root@hadoop hadoop]# hdfs dfs -ls -R /

drwxr-xr-x - root supergroup 0 2017-05-18 23:57 /Demo

-rw-r--r-- 1 root supergroup 3494 2017-05-18 23:57 /Demo/hadoop-env.sh

drwxr-xr-x - root supergroup 0 2017-05-18 19:01 /logs

-rw-r--r-- 1 root supergroup 2223 2017-05-18 19:01 /logs/anaconda-ks.cfg

-rw-r--r-- 1 root supergroup 57162 2017-05-18 18:32 /logs/install.log

创建HDFS连接实例

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#!/usr/bin/env python

# -*- coding:utf-8 -*-

__Author__ = 'kongZhaGen'

import hdfs

client = hdfs.Client("http://172.10.236.21:50070")

清单：返回远程文件夹包含的文件或目录名称，如果路径不存在则抛出错误。

　　hdfs_path：远程文件夹的路径

　　状态：同时返回每个文件的状态信息

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def list(self, hdfs_path, status=False):

"""Return names of files contained in a remote folder.

:param hdfs_path: Remote path to a directory. If `hdfs_path` doesn't exist

or points to a normal file, an :class:`HdfsError` will be raised.

:param status: Also return each file's corresponding FileStatus_.

"""

　　示例：

print client.list("/",status=False)

结果：

[u'Demo', u'logs']

状态：获取HDFS系统上文件或文件夹的状态信息

　　hdfs_path：路径名称

　　严格：

　　　　假：如果远程路径不存在返回无

　　　　真：如果远程路径不存在抛出异常

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def status(self, hdfs_path, strict=True):

"""Get FileStatus_ for a file or folder on HDFS.

:param hdfs_path: Remote path.

:param strict: If `False`, return `None` rather than raise an exception if

the path doesn't exist.

.. _FileStatus: FS_

.. _FS: http://hadoop.apache.org/docs/r1.0.4/webhdfs.html#FileStatus

"""

　　示例：

print client.status(hdfs_path="/Demoo",strict=False)

结果：

None

makedirs：在HDFS上创建目录，可实现递归创建目录

　　hdfs_path：远程目录名称

　　许可：为新创建的目录设置权限

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def makedirs(self, hdfs_path, permission=None):

"""Create a remote directory, recursively if necessary.

:param hdfs_path: Remote path. Intermediate directories will be created

appropriately.

:param permission: Octal permission to set on the newly created directory.

These permissions will only be set on directories that do not already

exist.

This function currently has no return value as WebHDFS doesn't return a

meaningful flag.

"""

　　示例：

　　如果想在远程客户端通过脚本给HDFS创建目录，需要修改HDFS-site.xml中中中中

<property>

<name>dfs.permissions</name>

<value>false</value>

</property>

　　重启HDFS

1 2	`stop-dfs.sh` `start-dfs.sh`

　　递归创建目录

1	`client.makedirs("/data/rar/tmp",permission=755)`

重命名：移动一个文件或文件夹

　　hdfs_src_path：源路径

　　hdfs_dst_path：目标路径，如果路径存在且是个目录，则源目录移动到此目录中如果路径存在且是个文件，则会抛出异常

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def rename(self, hdfs_src_path, hdfs_dst_path):

"""Move a file or folder.

:param hdfs_src_path: Source path.

:param hdfs_dst_path: Destination path. If the path already exists and is

a directory, the source will be moved into it. If the path exists and is

a file, or if a parent destination directory is missing, this method will

raise an :class:`HdfsError`.

"""

　　示例：

1	`client.rename("/SRC_DATA","/dest_data")`

删除：从HDFS删除一个文件或目录

　　hdfs_path：HDFS系统上的路径

　　递归：如果目录非空，真：可递归删除.FALSE：抛出异常。

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def delete(self, hdfs_path, recursive=False):

"""Remove a file or directory from HDFS.

:param hdfs_path: HDFS path.

:param recursive: Recursively delete files and directories. By default,

this method will raise an :class:`HdfsError` if trying to delete a

non-empty directory.

This function returns `True` if the deletion was successful and `False` if

no file or directory previously existed at `hdfs_path`.

"""

　　示例：

1	`client.delete("/dest_data",recursive=True)`

上传：上传文件或目录到HDFS文件系统，如果目标目录已经存在，则将文件或目录上传到此目录中，否则新建目录。

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def upload(self, hdfs_path, local_path, overwrite=False, n_threads=1,

temp_dir=None, chunk_size=2 ** 16, progress=None, cleanup=True, **kwargs):

"""Upload a file or directory to HDFS.

:param hdfs_path: Target HDFS path. If it already exists and is a

directory, files will be uploaded inside.

:param local_path: Local path to file or folder. If a folder, all the files

inside of it will be uploaded (note that this implies that folders empty

of files will not be created remotely).

:param overwrite: Overwrite any existing file or directory.

:param n_threads: Number of threads to use for parallelization. A value of

`0` (or negative) uses as many threads as there are files.

:param temp_dir: Directory under which the files will first be uploaded

when `overwrite=True` and the final remote path already exists. Once the

upload successfully completes, it will be swapped in.

:param chunk_size: Interval in bytes by which the files will be uploaded.

:param progress: Callback function to track progress, called every

`chunk_size` bytes. It will be passed two arguments, the path to the

file being uploaded and the number of bytes transferred so far. On

completion, it will be called once with `-1` as second argument.

:param cleanup: Delete any uploaded files if an error occurs during the

upload.

:param \*\*kwargs: Keyword arguments forwarded to :meth:`write`.

On success, this method returns the remote upload path.

"""

　　示例：

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>>> import hdfs

>>> client=hdfs.Client("http://172.10.236.21:50070")

>>> client.upload("/logs","/root/training/jdk-7u75-linux-i586.tar.gz")

'/logs/jdk-7u75-linux-i586.tar.gz'

>>> client.list("/logs")

[u'anaconda-ks.cfg', u'install.log', u'jdk-7u75-linux-i586.tar.gz']

内容：获取HDFS系统上文件或目录的概要信息

print client.content("/logs/install.log")

结果：

{u'spaceConsumed': 57162, u'quota': -1, u'spaceQuota': -1, u'length': 57162, u'directoryCount': 0, u'fileCount': 1}

写：在HDFS文件系统上创建文件，可以是字符串，生成器或文件对象

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def write(self, hdfs_path, data=None, overwrite=False, permission=None,

blocksize=None, replication=None, buffersize=None, append=False,

encoding=None):

"""Create a file on HDFS.

:param hdfs_path: Path where to create file. The necessary directories will

be created appropriately.

:param data: Contents of file to write. Can be a string, a generator or a

file object. The last two options will allow streaming upload (i.e.

without having to load the entire contents into memory). If `None`, this

method will return a file-like object and should be called using a `with`

block (see below for examples).

:param overwrite: Overwrite any existing file or directory.

:param permission: Octal permission to set on the newly created file.

Leading zeros may be omitted.

:param blocksize: Block size of the file.

:param replication: Number of replications of the file.

:param buffersize: Size of upload buffer.

:param append: Append to a file rather than create a new one.

:param encoding: Encoding used to serialize data written.

"""

原文见：HTTP：//www.cnblogs.com/kongzhagen/p/6874111.html