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| <div class="section" id="filesystem-interface"> |
| <span id="filesystem"></span><h1>Filesystem Interface<a class="headerlink" href="#filesystem-interface" title="Permalink to this headline">¶</a></h1> |
| <p>PyArrow comes with an abstract filesystem interface, as well as concrete |
| implementations for various storage types.</p> |
| <p>The filesystem interface provides input and output streams as well as |
| directory operations. A simplified view of the underlying data |
| storage is exposed. Data paths are represented as <em>abstract paths</em>, which |
| are <code class="docutils literal notranslate"><span class="pre">/</span></code>-separated, even on Windows, and shouldn’t include special path |
| components such as <code class="docutils literal notranslate"><span class="pre">.</span></code> and <code class="docutils literal notranslate"><span class="pre">..</span></code>. Symbolic links, if supported by the |
| underlying storage, are automatically dereferenced. Only basic |
| <a class="reference internal" href="generated/pyarrow.fs.FileInfo.html#pyarrow.fs.FileInfo" title="pyarrow.fs.FileInfo"><code class="xref py py-class docutils literal notranslate"><span class="pre">metadata</span></code></a> about file entries, such as the file size |
| and modification time, is made available.</p> |
| <p>The core interface is represented by the base class <a class="reference internal" href="generated/pyarrow.fs.FileSystem.html#pyarrow.fs.FileSystem" title="pyarrow.fs.FileSystem"><code class="xref py py-class docutils literal notranslate"><span class="pre">FileSystem</span></code></a>. |
| Concrete subclasses are available for various kinds of storage, such as local |
| filesystem access (<a class="reference internal" href="generated/pyarrow.fs.LocalFileSystem.html#pyarrow.fs.LocalFileSystem" title="pyarrow.fs.LocalFileSystem"><code class="xref py py-class docutils literal notranslate"><span class="pre">LocalFileSystem</span></code></a>), HDFS (<a class="reference internal" href="generated/pyarrow.fs.HadoopFileSystem.html#pyarrow.fs.HadoopFileSystem" title="pyarrow.fs.HadoopFileSystem"><code class="xref py py-class docutils literal notranslate"><span class="pre">HadoopFileSystem</span></code></a>) |
| and Amazon S3-compatible storage (<code class="xref py py-class docutils literal notranslate"><span class="pre">S3FileSystem</span></code>).</p> |
| <div class="section" id="usage"> |
| <h2>Usage<a class="headerlink" href="#usage" title="Permalink to this headline">¶</a></h2> |
| <p>A FileSystem object can be created with one of the constructors (and check the |
| respective constructor for its options):</p> |
| <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">pyarrow</span> <span class="k">import</span> <span class="n">fs</span> |
| <span class="gp">>>> </span><span class="n">local</span> <span class="o">=</span> <span class="n">fs</span><span class="o">.</span><span class="n">LocalFileSystem</span><span class="p">()</span> |
| </pre></div> |
| </div> |
| <p>or alternatively inferred from a URI:</p> |
| <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">s3</span><span class="p">,</span> <span class="n">path</span> <span class="o">=</span> <span class="n">fs</span><span class="o">.</span><span class="n">FileSystem</span><span class="o">.</span><span class="n">from_uri</span><span class="p">(</span><span class="s2">"s3://my-bucket"</span><span class="p">)</span> |
| <span class="gp">>>> </span><span class="n">s3</span> |
| <span class="go"><pyarrow._s3fs.S3FileSystem at 0x7f6760cbf4f0></span> |
| <span class="gp">>>> </span><span class="n">path</span> |
| <span class="go">'my-bucket'</span> |
| </pre></div> |
| </div> |
| <div class="section" id="reading-and-writing-files"> |
| <h3>Reading and writing files<a class="headerlink" href="#reading-and-writing-files" title="Permalink to this headline">¶</a></h3> |
| <p>Several of the IO-related functions in PyArrow accept either a URI (and infer |
| the filesystem) or an explicit <code class="docutils literal notranslate"><span class="pre">filesystem</span></code> argument to specify the filesystem |
| to read or write from. For example, the <a class="reference internal" href="generated/pyarrow.parquet.read_table.html#pyarrow.parquet.read_table" title="pyarrow.parquet.read_table"><code class="xref py py-meth docutils literal notranslate"><span class="pre">pyarrow.parquet.read_table()</span></code></a> |
| function can be used in the following ways:</p> |
| <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="c1"># using a URI -> filesystem is inferred</span> |
| <span class="n">pq</span><span class="o">.</span><span class="n">read_table</span><span class="p">(</span><span class="s2">"s3://my-bucket/data.parquet"</span><span class="p">)</span> |
| <span class="c1"># using a path and filesystem</span> |
| <span class="n">s3</span> <span class="o">=</span> <span class="n">fs</span><span class="o">.</span><span class="n">S3FileSystem</span><span class="p">(</span><span class="o">..</span><span class="p">)</span> |
| <span class="n">pq</span><span class="o">.</span><span class="n">read_table</span><span class="p">(</span><span class="s2">"my-bucket/data.parquet"</span><span class="p">,</span> <span class="n">filesystem</span><span class="o">=</span><span class="n">s3</span><span class="p">)</span> |
| </pre></div> |
| </div> |
| <p>The filesystem interface further allows to open files for reading (input) or |
| writing (output) directly, which can be combined with functions that work with |
| file-like objects. For example:</p> |
| <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">local</span> <span class="o">=</span> <span class="n">fs</span><span class="o">.</span><span class="n">LocalFileSystem</span><span class="p">()</span> |
| |
| <span class="k">with</span> <span class="n">local</span><span class="o">.</span><span class="n">open_output_stream</span><span class="p">(</span><span class="s2">"test.arrow"</span><span class="p">)</span> <span class="k">as</span> <span class="n">file</span><span class="p">:</span> |
| <span class="k">with</span> <span class="n">pa</span><span class="o">.</span><span class="n">RecordBatchFileWriter</span><span class="p">(</span><span class="n">file</span><span class="p">,</span> <span class="n">table</span><span class="o">.</span><span class="n">schema</span><span class="p">)</span> <span class="k">as</span> <span class="n">writer</span><span class="p">:</span> |
| <span class="n">writer</span><span class="o">.</span><span class="n">write_table</span><span class="p">(</span><span class="n">table</span><span class="p">)</span> |
| </pre></div> |
| </div> |
| </div> |
| <div class="section" id="listing-files"> |
| <h3>Listing files<a class="headerlink" href="#listing-files" title="Permalink to this headline">¶</a></h3> |
| <p>Inspecting the directories and files on a filesystem can be done with the |
| <a class="reference internal" href="generated/pyarrow.fs.FileSystem.html#pyarrow.fs.FileSystem.get_file_info" title="pyarrow.fs.FileSystem.get_file_info"><code class="xref py py-meth docutils literal notranslate"><span class="pre">FileSystem.get_file_info()</span></code></a> method. To list the contents of a directory, |
| use the <a class="reference internal" href="generated/pyarrow.fs.FileSelector.html#pyarrow.fs.FileSelector" title="pyarrow.fs.FileSelector"><code class="xref py py-class docutils literal notranslate"><span class="pre">FileSelector</span></code></a> object to specify the selection:</p> |
| <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">local</span><span class="o">.</span><span class="n">get_file_info</span><span class="p">(</span><span class="n">fs</span><span class="o">.</span><span class="n">FileSelector</span><span class="p">(</span><span class="s2">"dataset/"</span><span class="p">,</span> <span class="n">recursive</span><span class="o">=</span><span class="kc">True</span><span class="p">))</span> |
| <span class="go">[<FileInfo for 'dataset/part=B': type=FileType.Directory>,</span> |
| <span class="go"> <FileInfo for 'dataset/part=B/data0.parquet': type=FileType.File, size=1564>,</span> |
| <span class="go"> <FileInfo for 'dataset/part=A': type=FileType.Directory>,</span> |
| <span class="go"> <FileInfo for 'dataset/part=A/data0.parquet': type=FileType.File, size=1564>]</span> |
| </pre></div> |
| </div> |
| <p>This returns a list of <a class="reference internal" href="generated/pyarrow.fs.FileInfo.html#pyarrow.fs.FileInfo" title="pyarrow.fs.FileInfo"><code class="xref py py-class docutils literal notranslate"><span class="pre">FileInfo</span></code></a> objects, containing information about |
| the type (file or directory), the size, the date last modified, etc.</p> |
| <p>You can also get this information for a single explicit path (or list of |
| paths):</p> |
| <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">local</span><span class="o">.</span><span class="n">get_file_info</span><span class="p">(</span><span class="s1">'test.arrow'</span><span class="p">)</span> |
| <span class="go"><FileInfo for 'test.arrow': type=FileType.File, size=3250></span> |
| |
| <span class="gp">>>> </span><span class="n">local</span><span class="o">.</span><span class="n">get_file_info</span><span class="p">(</span><span class="s1">'non_existent'</span><span class="p">)</span> |
| <span class="go"><FileInfo for 'non_existent': type=FileType.NotFound></span> |
| </pre></div> |
| </div> |
| </div> |
| </div> |
| <div class="section" id="s3"> |
| <h2>S3<a class="headerlink" href="#s3" title="Permalink to this headline">¶</a></h2> |
| <p>The <code class="xref py py-class docutils literal notranslate"><span class="pre">S3FileSystem</span></code> constructor has several options to configure the S3 |
| connection (e.g. credentials, the region, an endpoint override, etc). In |
| addition, the constructor will also inspect configured S3 credentials as |
| supported by AWS (for example the <code class="docutils literal notranslate"><span class="pre">AWS_ACCESS_KEY_ID</span></code> and |
| <code class="docutils literal notranslate"><span class="pre">AWS_SECRET_ACCESS_KEY</span></code> environment variables).</p> |
| <p>Example how you can read contents from a S3 bucket:</p> |
| <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">pyarrow</span> <span class="k">import</span> <span class="n">fs</span> |
| <span class="gp">>>> </span><span class="n">s3</span> <span class="o">=</span> <span class="n">fs</span><span class="o">.</span><span class="n">S3FileSystem</span><span class="p">(</span><span class="n">region</span><span class="o">=</span><span class="s1">'eu-west-3'</span><span class="p">)</span> |
| |
| <span class="go"># List all contents in a bucket, recursively</span> |
| <span class="gp">>>> </span><span class="n">s3</span><span class="o">.</span><span class="n">get_file_info</span><span class="p">(</span><span class="n">fs</span><span class="o">.</span><span class="n">FileSelector</span><span class="p">(</span><span class="s1">'my-test-bucket'</span><span class="p">,</span> <span class="n">recursive</span><span class="o">=</span><span class="kc">True</span><span class="p">))</span> |
| <span class="go">[<FileInfo for 'my-test-bucket/File1': type=FileType.File, size=10>,</span> |
| <span class="go"> <FileInfo for 'my-test-bucket/File5': type=FileType.File, size=10>,</span> |
| <span class="go"> <FileInfo for 'my-test-bucket/Dir1': type=FileType.Directory>,</span> |
| <span class="go"> <FileInfo for 'my-test-bucket/Dir2': type=FileType.Directory>,</span> |
| <span class="go"> <FileInfo for 'my-test-bucket/EmptyDir': type=FileType.Directory>,</span> |
| <span class="go"> <FileInfo for 'my-test-bucket/Dir1/File2': type=FileType.File, size=11>,</span> |
| <span class="go"> <FileInfo for 'my-test-bucket/Dir1/Subdir': type=FileType.Directory>,</span> |
| <span class="go"> <FileInfo for 'my-test-bucket/Dir2/Subdir': type=FileType.Directory>,</span> |
| <span class="go"> <FileInfo for 'my-test-bucket/Dir2/Subdir/File3': type=FileType.File, size=10>]</span> |
| |
| <span class="go"># Open a file for reading and download its contents</span> |
| <span class="gp">>>> </span><span class="n">f</span> <span class="o">=</span> <span class="n">s3</span><span class="o">.</span><span class="n">open_input_stream</span><span class="p">(</span><span class="s1">'my-test-bucket/Dir1/File2'</span><span class="p">)</span> |
| <span class="gp">>>> </span><span class="n">f</span><span class="o">.</span><span class="n">readall</span><span class="p">()</span> |
| <span class="go">b'some data'</span> |
| </pre></div> |
| </div> |
| <div class="admonition seealso"> |
| <p class="admonition-title">See also</p> |
| <p>See the <a class="reference external" href="https://docs.aws.amazon.com/sdk-for-cpp/v1/developer-guide/credentials.html">AWS docs</a> |
| for the different ways to configure the AWS credentials.</p> |
| </div> |
| </div> |
| <div class="section" id="hadoop-file-system-hdfs"> |
| <h2>Hadoop File System (HDFS)<a class="headerlink" href="#hadoop-file-system-hdfs" title="Permalink to this headline">¶</a></h2> |
| <p>PyArrow comes with bindings to the Hadoop File System (based on C++ bindings |
| using <code class="docutils literal notranslate"><span class="pre">libhdfs</span></code>, a JNI-based interface to the Java Hadoop client). You connect |
| using the <a class="reference internal" href="generated/pyarrow.fs.HadoopFileSystem.html#pyarrow.fs.HadoopFileSystem" title="pyarrow.fs.HadoopFileSystem"><code class="xref py py-class docutils literal notranslate"><span class="pre">HadoopFileSystem</span></code></a> constructor:</p> |
| <div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">pyarrow</span> <span class="kn">import</span> <span class="n">fs</span> |
| <span class="n">hdfs</span> <span class="o">=</span> <span class="n">fs</span><span class="o">.</span><span class="n">HadoopFileSystem</span><span class="p">(</span><span class="n">host</span><span class="p">,</span> <span class="n">port</span><span class="p">,</span> <span class="n">user</span><span class="o">=</span><span class="n">user</span><span class="p">,</span> <span class="n">kerb_ticket</span><span class="o">=</span><span class="n">ticket_cache_path</span><span class="p">)</span> |
| </pre></div> |
| </div> |
| <p>The <code class="docutils literal notranslate"><span class="pre">libhdfs</span></code> library is loaded <strong>at runtime</strong> (rather than at link / library |
| load time, since the library may not be in your LD_LIBRARY_PATH), and relies on |
| some environment variables.</p> |
| <ul> |
| <li><p><code class="docutils literal notranslate"><span class="pre">HADOOP_HOME</span></code>: the root of your installed Hadoop distribution. Often has |
| <cite>lib/native/libhdfs.so</cite>.</p></li> |
| <li><p><code class="docutils literal notranslate"><span class="pre">JAVA_HOME</span></code>: the location of your Java SDK installation.</p></li> |
| <li><p><code class="docutils literal notranslate"><span class="pre">ARROW_LIBHDFS_DIR</span></code> (optional): explicit location of <code class="docutils literal notranslate"><span class="pre">libhdfs.so</span></code> if it is |
| installed somewhere other than <code class="docutils literal notranslate"><span class="pre">$HADOOP_HOME/lib/native</span></code>.</p></li> |
| <li><p><code class="docutils literal notranslate"><span class="pre">CLASSPATH</span></code>: must contain the Hadoop jars. You can set these using:</p> |
| <div class="highlight-shell notranslate"><div class="highlight"><pre><span></span><span class="nb">export</span> <span class="nv">CLASSPATH</span><span class="o">=</span><span class="sb">`</span><span class="nv">$HADOOP_HOME</span>/bin/hdfs classpath --glob<span class="sb">`</span> |
| </pre></div> |
| </div> |
| <p>If <code class="docutils literal notranslate"><span class="pre">CLASSPATH</span></code> is not set, then it will be set automatically if the |
| <code class="docutils literal notranslate"><span class="pre">hadoop</span></code> executable is in your system path, or if <code class="docutils literal notranslate"><span class="pre">HADOOP_HOME</span></code> is set.</p> |
| </li> |
| </ul> |
| </div> |
| <div class="section" id="using-fsspec-compatible-filesystems"> |
| <h2>Using fsspec-compatible filesystems<a class="headerlink" href="#using-fsspec-compatible-filesystems" title="Permalink to this headline">¶</a></h2> |
| <p>The filesystems mentioned above are natively supported by Arrow C++ / PyArrow. |
| The Python ecosystem, however, also has several filesystem packages. Those |
| packages following the |
| <a class="reference external" href="https://filesystem-spec.readthedocs.io/en/latest/">fsspec</a> interface can be |
| used in PyArrow as well.</p> |
| <p>Functions accepting a filesystem object will also accept an fsspec subclass. |
| For example:</p> |
| <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="c1"># creating an fsspec-based filesystem object for Google Cloud Storage</span> |
| <span class="kn">import</span> <span class="nn">gcsfs</span> |
| <span class="n">fs</span> <span class="o">=</span> <span class="n">gcsfs</span><span class="o">.</span><span class="n">GCSFileSystem</span><span class="p">(</span><span class="n">project</span><span class="o">=</span><span class="s1">'my-google-project'</span><span class="p">)</span> |
| |
| <span class="c1"># using this to read a partitioned dataset</span> |
| <span class="kn">import</span> <span class="nn">pyarrow.dataset</span> <span class="k">as</span> <span class="nn">ds</span> |
| <span class="n">ds</span><span class="o">.</span><span class="n">dataset</span><span class="p">(</span><span class="s2">"data/"</span><span class="p">,</span> <span class="n">filesystem</span><span class="o">=</span><span class="n">fs</span><span class="p">)</span> |
| </pre></div> |
| </div> |
| <p>Under the hood, the fsspec filesystem object is wrapped into a python-based |
| PyArrow filesystem (<a class="reference internal" href="generated/pyarrow.fs.PyFileSystem.html#pyarrow.fs.PyFileSystem" title="pyarrow.fs.PyFileSystem"><code class="xref py py-class docutils literal notranslate"><span class="pre">PyFileSystem</span></code></a>) using <a class="reference internal" href="generated/pyarrow.fs.FSSpecHandler.html#pyarrow.fs.FSSpecHandler" title="pyarrow.fs.FSSpecHandler"><code class="xref py py-class docutils literal notranslate"><span class="pre">FSSpecHandler</span></code></a>. |
| You can also manually do this to get an object with the PyArrow FileSystem |
| interface:</p> |
| <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">pyarrow.fs</span> <span class="k">import</span> <span class="n">PyFileSystem</span><span class="p">,</span> <span class="n">FSSpecHandler</span> |
| <span class="n">pa_fs</span> <span class="o">=</span> <span class="n">PyFileSystem</span><span class="p">(</span><span class="n">FSSpecHandler</span><span class="p">(</span><span class="n">fs</span><span class="p">))</span> |
| </pre></div> |
| </div> |
| </div> |
| </div> |
| |
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