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<li><a class="reference internal" href="#">Utilities for Developers</a><ul>
<li><a class="reference internal" href="#validation-tools">Validation Tools</a></li>
<li><a class="reference internal" href="#efficient-linear-algebra-array-operations">Efficient Linear Algebra & Array Operations</a></li>
<li><a class="reference internal" href="#efficient-random-sampling">Efficient Random Sampling</a></li>
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<section id="utilities-for-developers">
<span id="developers-utils"></span><h1>Utilities for Developers<a class="headerlink" href="#utilities-for-developers" title="Permalink to this heading">¶</a></h1>
<p>Scikit-learn contains a number of utilities to help with development. These are
located in <a class="reference internal" href="../modules/classes.html#module-sklearn.utils" title="sklearn.utils"><code class="xref py py-mod docutils literal notranslate"><span class="pre">sklearn.utils</span></code></a>, and include tools in a number of categories.
All the following functions and classes are in the module <a class="reference internal" href="../modules/classes.html#module-sklearn.utils" title="sklearn.utils"><code class="xref py py-mod docutils literal notranslate"><span class="pre">sklearn.utils</span></code></a>.</p>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>These utilities are meant to be used internally within the scikit-learn
package. They are not guaranteed to be stable between versions of
scikit-learn. Backports, in particular, will be removed as the scikit-learn
dependencies evolve.</p>
</div>
<section id="validation-tools">
<h2>Validation Tools<a class="headerlink" href="#validation-tools" title="Permalink to this heading">¶</a></h2>
<p>These are tools used to check and validate input. When you write a function
which accepts arrays, matrices, or sparse matrices as arguments, the following
should be used when applicable.</p>
<ul class="simple">
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.assert_all_finite.html#sklearn.utils.assert_all_finite" title="sklearn.utils.assert_all_finite"><code class="xref py py-func docutils literal notranslate"><span class="pre">assert_all_finite</span></code></a>: Throw an error if array contains NaNs or Infs.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.as_float_array.html#sklearn.utils.as_float_array" title="sklearn.utils.as_float_array"><code class="xref py py-func docutils literal notranslate"><span class="pre">as_float_array</span></code></a>: convert input to an array of floats. If a sparse
matrix is passed, a sparse matrix will be returned.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.check_array.html#sklearn.utils.check_array" title="sklearn.utils.check_array"><code class="xref py py-func docutils literal notranslate"><span class="pre">check_array</span></code></a>: check that input is a 2D array, raise error on sparse
matrices. Allowed sparse matrix formats can be given optionally, as well as
allowing 1D or N-dimensional arrays. Calls <a class="reference internal" href="../modules/generated/sklearn.utils.assert_all_finite.html#sklearn.utils.assert_all_finite" title="sklearn.utils.assert_all_finite"><code class="xref py py-func docutils literal notranslate"><span class="pre">assert_all_finite</span></code></a> by
default.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.check_X_y.html#sklearn.utils.check_X_y" title="sklearn.utils.check_X_y"><code class="xref py py-func docutils literal notranslate"><span class="pre">check_X_y</span></code></a>: check that X and y have consistent length, calls
check_array on X, and column_or_1d on y. For multilabel classification or
multitarget regression, specify multi_output=True, in which case check_array
will be called on y.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.indexable.html#sklearn.utils.indexable" title="sklearn.utils.indexable"><code class="xref py py-func docutils literal notranslate"><span class="pre">indexable</span></code></a>: check that all input arrays have consistent length and can
be sliced or indexed using safe_index. This is used to validate input for
cross-validation.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.validation.check_memory.html#sklearn.utils.validation.check_memory" title="sklearn.utils.validation.check_memory"><code class="xref py py-func docutils literal notranslate"><span class="pre">validation.check_memory</span></code></a> checks that input is <code class="docutils literal notranslate"><span class="pre">joblib.Memory</span></code>-like,
which means that it can be converted into a
<code class="docutils literal notranslate"><span class="pre">sklearn.utils.Memory</span></code> instance (typically a str denoting
the <code class="docutils literal notranslate"><span class="pre">cachedir</span></code>) or has the same interface.</p></li>
</ul>
<p>If your code relies on a random number generator, it should never use
functions like <code class="docutils literal notranslate"><span class="pre">numpy.random.random</span></code> or <code class="docutils literal notranslate"><span class="pre">numpy.random.normal</span></code>. This
approach can lead to repeatability issues in unit tests. Instead, a
<code class="docutils literal notranslate"><span class="pre">numpy.random.RandomState</span></code> object should be used, which is built from
a <code class="docutils literal notranslate"><span class="pre">random_state</span></code> argument passed to the class or function. The function
<a class="reference internal" href="../modules/generated/sklearn.utils.check_random_state.html#sklearn.utils.check_random_state" title="sklearn.utils.check_random_state"><code class="xref py py-func docutils literal notranslate"><span class="pre">check_random_state</span></code></a>, below, can then be used to create a random
number generator object.</p>
<ul class="simple">
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.check_random_state.html#sklearn.utils.check_random_state" title="sklearn.utils.check_random_state"><code class="xref py py-func docutils literal notranslate"><span class="pre">check_random_state</span></code></a>: create a <code class="docutils literal notranslate"><span class="pre">np.random.RandomState</span></code> object from
a parameter <code class="docutils literal notranslate"><span class="pre">random_state</span></code>.</p>
<ul>
<li><p>If <code class="docutils literal notranslate"><span class="pre">random_state</span></code> is <code class="docutils literal notranslate"><span class="pre">None</span></code> or <code class="docutils literal notranslate"><span class="pre">np.random</span></code>, then a
randomly-initialized <code class="docutils literal notranslate"><span class="pre">RandomState</span></code> object is returned.</p></li>
<li><p>If <code class="docutils literal notranslate"><span class="pre">random_state</span></code> is an integer, then it is used to seed a new
<code class="docutils literal notranslate"><span class="pre">RandomState</span></code> object.</p></li>
<li><p>If <code class="docutils literal notranslate"><span class="pre">random_state</span></code> is a <code class="docutils literal notranslate"><span class="pre">RandomState</span></code> object, then it is passed through.</p></li>
</ul>
</li>
</ul>
<p>For example:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">sklearn.utils</span> <span class="kn">import</span> <span class="n">check_random_state</span>
<span class="gp">>>> </span><span class="n">random_state</span> <span class="o">=</span> <span class="mi">0</span>
<span class="gp">>>> </span><span class="n">random_state</span> <span class="o">=</span> <span class="n">check_random_state</span><span class="p">(</span><span class="n">random_state</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">random_state</span><span class="o">.</span><span class="n">rand</span><span class="p">(</span><span class="mi">4</span><span class="p">)</span>
<span class="go">array([0.5488135 , 0.71518937, 0.60276338, 0.54488318])</span>
</pre></div>
</div>
<p>When developing your own scikit-learn compatible estimator, the following
helpers are available.</p>
<ul class="simple">
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.validation.check_is_fitted.html#sklearn.utils.validation.check_is_fitted" title="sklearn.utils.validation.check_is_fitted"><code class="xref py py-func docutils literal notranslate"><span class="pre">validation.check_is_fitted</span></code></a>: check that the estimator has been fitted
before calling <code class="docutils literal notranslate"><span class="pre">transform</span></code>, <code class="docutils literal notranslate"><span class="pre">predict</span></code>, or similar methods. This helper
allows to raise a standardized error message across estimator.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.validation.has_fit_parameter.html#sklearn.utils.validation.has_fit_parameter" title="sklearn.utils.validation.has_fit_parameter"><code class="xref py py-func docutils literal notranslate"><span class="pre">validation.has_fit_parameter</span></code></a>: check that a given parameter is
supported in the <code class="docutils literal notranslate"><span class="pre">fit</span></code> method of a given estimator.</p></li>
</ul>
</section>
<section id="efficient-linear-algebra-array-operations">
<h2>Efficient Linear Algebra & Array Operations<a class="headerlink" href="#efficient-linear-algebra-array-operations" title="Permalink to this heading">¶</a></h2>
<ul class="simple">
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.extmath.randomized_range_finder.html#sklearn.utils.extmath.randomized_range_finder" title="sklearn.utils.extmath.randomized_range_finder"><code class="xref py py-func docutils literal notranslate"><span class="pre">extmath.randomized_range_finder</span></code></a>: construct an orthonormal matrix
whose range approximates the range of the input. This is used in
<a class="reference internal" href="../modules/generated/sklearn.utils.extmath.randomized_svd.html#sklearn.utils.extmath.randomized_svd" title="sklearn.utils.extmath.randomized_svd"><code class="xref py py-func docutils literal notranslate"><span class="pre">extmath.randomized_svd</span></code></a>, below.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.extmath.randomized_svd.html#sklearn.utils.extmath.randomized_svd" title="sklearn.utils.extmath.randomized_svd"><code class="xref py py-func docutils literal notranslate"><span class="pre">extmath.randomized_svd</span></code></a>: compute the k-truncated randomized SVD.
This algorithm finds the exact truncated singular values decomposition
using randomization to speed up the computations. It is particularly
fast on large matrices on which you wish to extract only a small
number of components.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">arrayfuncs.cholesky_delete</span></code>:
(used in <a class="reference internal" href="../modules/generated/sklearn.linear_model.lars_path.html#sklearn.linear_model.lars_path" title="sklearn.linear_model.lars_path"><code class="xref py py-func docutils literal notranslate"><span class="pre">lars_path</span></code></a>) Remove an
item from a cholesky factorization.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.arrayfuncs.min_pos.html#sklearn.utils.arrayfuncs.min_pos" title="sklearn.utils.arrayfuncs.min_pos"><code class="xref py py-func docutils literal notranslate"><span class="pre">arrayfuncs.min_pos</span></code></a>: (used in <code class="docutils literal notranslate"><span class="pre">sklearn.linear_model.least_angle</span></code>)
Find the minimum of the positive values within an array.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.extmath.fast_logdet.html#sklearn.utils.extmath.fast_logdet" title="sklearn.utils.extmath.fast_logdet"><code class="xref py py-func docutils literal notranslate"><span class="pre">extmath.fast_logdet</span></code></a>: efficiently compute the log of the determinant
of a matrix.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.extmath.density.html#sklearn.utils.extmath.density" title="sklearn.utils.extmath.density"><code class="xref py py-func docutils literal notranslate"><span class="pre">extmath.density</span></code></a>: efficiently compute the density of a sparse vector</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.extmath.safe_sparse_dot.html#sklearn.utils.extmath.safe_sparse_dot" title="sklearn.utils.extmath.safe_sparse_dot"><code class="xref py py-func docutils literal notranslate"><span class="pre">extmath.safe_sparse_dot</span></code></a>: dot product which will correctly handle
<code class="docutils literal notranslate"><span class="pre">scipy.sparse</span></code> inputs. If the inputs are dense, it is equivalent to
<code class="docutils literal notranslate"><span class="pre">numpy.dot</span></code>.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.extmath.weighted_mode.html#sklearn.utils.extmath.weighted_mode" title="sklearn.utils.extmath.weighted_mode"><code class="xref py py-func docutils literal notranslate"><span class="pre">extmath.weighted_mode</span></code></a>: an extension of <code class="docutils literal notranslate"><span class="pre">scipy.stats.mode</span></code> which
allows each item to have a real-valued weight.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.resample.html#sklearn.utils.resample" title="sklearn.utils.resample"><code class="xref py py-func docutils literal notranslate"><span class="pre">resample</span></code></a>: Resample arrays or sparse matrices in a consistent way.
used in <a class="reference internal" href="../modules/generated/sklearn.utils.shuffle.html#sklearn.utils.shuffle" title="sklearn.utils.shuffle"><code class="xref py py-func docutils literal notranslate"><span class="pre">shuffle</span></code></a>, below.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.shuffle.html#sklearn.utils.shuffle" title="sklearn.utils.shuffle"><code class="xref py py-func docutils literal notranslate"><span class="pre">shuffle</span></code></a>: Shuffle arrays or sparse matrices in a consistent way.
Used in <a class="reference internal" href="../modules/generated/sklearn.cluster.k_means.html#sklearn.cluster.k_means" title="sklearn.cluster.k_means"><code class="xref py py-func docutils literal notranslate"><span class="pre">k_means</span></code></a>.</p></li>
</ul>
</section>
<section id="efficient-random-sampling">
<h2>Efficient Random Sampling<a class="headerlink" href="#efficient-random-sampling" title="Permalink to this heading">¶</a></h2>
<ul class="simple">
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.random.sample_without_replacement.html#sklearn.utils.random.sample_without_replacement" title="sklearn.utils.random.sample_without_replacement"><code class="xref py py-func docutils literal notranslate"><span class="pre">random.sample_without_replacement</span></code></a>: implements efficient algorithms
for sampling <code class="docutils literal notranslate"><span class="pre">n_samples</span></code> integers from a population of size <code class="docutils literal notranslate"><span class="pre">n_population</span></code>
without replacement.</p></li>
</ul>
</section>
<section id="efficient-routines-for-sparse-matrices">
<h2>Efficient Routines for Sparse Matrices<a class="headerlink" href="#efficient-routines-for-sparse-matrices" title="Permalink to this heading">¶</a></h2>
<p>The <code class="docutils literal notranslate"><span class="pre">sklearn.utils.sparsefuncs</span></code> cython module hosts compiled extensions to
efficiently process <code class="docutils literal notranslate"><span class="pre">scipy.sparse</span></code> data.</p>
<ul class="simple">
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.sparsefuncs.mean_variance_axis.html#sklearn.utils.sparsefuncs.mean_variance_axis" title="sklearn.utils.sparsefuncs.mean_variance_axis"><code class="xref py py-func docutils literal notranslate"><span class="pre">sparsefuncs.mean_variance_axis</span></code></a>: compute the means and
variances along a specified axis of a CSR matrix.
Used for normalizing the tolerance stopping criterion in
<a class="reference internal" href="../modules/generated/sklearn.cluster.KMeans.html#sklearn.cluster.KMeans" title="sklearn.cluster.KMeans"><code class="xref py py-class docutils literal notranslate"><span class="pre">KMeans</span></code></a>.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.sparsefuncs_fast.inplace_csr_row_normalize_l1.html#sklearn.utils.sparsefuncs_fast.inplace_csr_row_normalize_l1" title="sklearn.utils.sparsefuncs_fast.inplace_csr_row_normalize_l1"><code class="xref py py-func docutils literal notranslate"><span class="pre">sparsefuncs_fast.inplace_csr_row_normalize_l1</span></code></a> and
<a class="reference internal" href="../modules/generated/sklearn.utils.sparsefuncs_fast.inplace_csr_row_normalize_l2.html#sklearn.utils.sparsefuncs_fast.inplace_csr_row_normalize_l2" title="sklearn.utils.sparsefuncs_fast.inplace_csr_row_normalize_l2"><code class="xref py py-func docutils literal notranslate"><span class="pre">sparsefuncs_fast.inplace_csr_row_normalize_l2</span></code></a>: can be used to normalize
individual sparse samples to unit L1 or L2 norm as done in
<a class="reference internal" href="../modules/generated/sklearn.preprocessing.Normalizer.html#sklearn.preprocessing.Normalizer" title="sklearn.preprocessing.Normalizer"><code class="xref py py-class docutils literal notranslate"><span class="pre">Normalizer</span></code></a>.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.sparsefuncs.inplace_csr_column_scale.html#sklearn.utils.sparsefuncs.inplace_csr_column_scale" title="sklearn.utils.sparsefuncs.inplace_csr_column_scale"><code class="xref py py-func docutils literal notranslate"><span class="pre">sparsefuncs.inplace_csr_column_scale</span></code></a>: can be used to multiply the
columns of a CSR matrix by a constant scale (one scale per column).
Used for scaling features to unit standard deviation in
<a class="reference internal" href="../modules/generated/sklearn.preprocessing.StandardScaler.html#sklearn.preprocessing.StandardScaler" title="sklearn.preprocessing.StandardScaler"><code class="xref py py-class docutils literal notranslate"><span class="pre">StandardScaler</span></code></a>.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.neighbors.sort_graph_by_row_values.html#sklearn.neighbors.sort_graph_by_row_values" title="sklearn.neighbors.sort_graph_by_row_values"><code class="xref py py-func docutils literal notranslate"><span class="pre">sort_graph_by_row_values</span></code></a>: can be used to sort a
CSR sparse matrix such that each row is stored with increasing values. This
is useful to improve efficiency when using precomputed sparse distance
matrices in estimators relying on nearest neighbors graph.</p></li>
</ul>
</section>
<section id="graph-routines">
<h2>Graph Routines<a class="headerlink" href="#graph-routines" title="Permalink to this heading">¶</a></h2>
<ul class="simple">
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.graph.single_source_shortest_path_length.html#sklearn.utils.graph.single_source_shortest_path_length" title="sklearn.utils.graph.single_source_shortest_path_length"><code class="xref py py-func docutils literal notranslate"><span class="pre">graph.single_source_shortest_path_length</span></code></a>:
(not currently used in scikit-learn)
Return the shortest path from a single source
to all connected nodes on a graph. Code is adapted from <a class="reference external" href="https://networkx.github.io/">networkx</a>.
If this is ever needed again, it would be far faster to use a single
iteration of Dijkstra’s algorithm from <code class="docutils literal notranslate"><span class="pre">graph_shortest_path</span></code>.</p></li>
</ul>
</section>
<section id="testing-functions">
<h2>Testing Functions<a class="headerlink" href="#testing-functions" title="Permalink to this heading">¶</a></h2>
<ul class="simple">
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.discovery.all_estimators.html#sklearn.utils.discovery.all_estimators" title="sklearn.utils.discovery.all_estimators"><code class="xref py py-func docutils literal notranslate"><span class="pre">discovery.all_estimators</span></code></a> : returns a list of all estimators in
scikit-learn to test for consistent behavior and interfaces.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.discovery.all_displays.html#sklearn.utils.discovery.all_displays" title="sklearn.utils.discovery.all_displays"><code class="xref py py-func docutils literal notranslate"><span class="pre">discovery.all_displays</span></code></a> : returns a list of all displays (related to
plotting API) in scikit-learn to test for consistent behavior and interfaces.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.discovery.all_functions.html#sklearn.utils.discovery.all_functions" title="sklearn.utils.discovery.all_functions"><code class="xref py py-func docutils literal notranslate"><span class="pre">discovery.all_functions</span></code></a> : returns a list all functions in
scikit-learn to test for consistent behavior and interfaces.</p></li>
</ul>
</section>
<section id="multiclass-and-multilabel-utility-function">
<h2>Multiclass and multilabel utility function<a class="headerlink" href="#multiclass-and-multilabel-utility-function" title="Permalink to this heading">¶</a></h2>
<ul class="simple">
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.multiclass.is_multilabel.html#sklearn.utils.multiclass.is_multilabel" title="sklearn.utils.multiclass.is_multilabel"><code class="xref py py-func docutils literal notranslate"><span class="pre">multiclass.is_multilabel</span></code></a>: Helper function to check if the task
is a multi-label classification one.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.multiclass.unique_labels.html#sklearn.utils.multiclass.unique_labels" title="sklearn.utils.multiclass.unique_labels"><code class="xref py py-func docutils literal notranslate"><span class="pre">multiclass.unique_labels</span></code></a>: Helper function to extract an ordered
array of unique labels from different formats of target.</p></li>
</ul>
</section>
<section id="helper-functions">
<h2>Helper Functions<a class="headerlink" href="#helper-functions" title="Permalink to this heading">¶</a></h2>
<ul class="simple">
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.gen_even_slices.html#sklearn.utils.gen_even_slices" title="sklearn.utils.gen_even_slices"><code class="xref py py-class docutils literal notranslate"><span class="pre">gen_even_slices</span></code></a>: generator to create <code class="docutils literal notranslate"><span class="pre">n</span></code>-packs of slices going up
to <code class="docutils literal notranslate"><span class="pre">n</span></code>. Used in <a class="reference internal" href="../modules/generated/sklearn.decomposition.dict_learning.html#sklearn.decomposition.dict_learning" title="sklearn.decomposition.dict_learning"><code class="xref py py-func docutils literal notranslate"><span class="pre">dict_learning</span></code></a> and
<a class="reference internal" href="../modules/generated/sklearn.cluster.k_means.html#sklearn.cluster.k_means" title="sklearn.cluster.k_means"><code class="xref py py-func docutils literal notranslate"><span class="pre">k_means</span></code></a>.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.gen_batches.html#sklearn.utils.gen_batches" title="sklearn.utils.gen_batches"><code class="xref py py-class docutils literal notranslate"><span class="pre">gen_batches</span></code></a>: generator to create slices containing batch size elements
from 0 to <code class="docutils literal notranslate"><span class="pre">n</span></code></p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.safe_mask.html#sklearn.utils.safe_mask" title="sklearn.utils.safe_mask"><code class="xref py py-func docutils literal notranslate"><span class="pre">safe_mask</span></code></a>: Helper function to convert a mask to the format expected
by the numpy array or scipy sparse matrix on which to use it (sparse
matrices support integer indices only while numpy arrays support both
boolean masks and integer indices).</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.safe_sqr.html#sklearn.utils.safe_sqr" title="sklearn.utils.safe_sqr"><code class="xref py py-func docutils literal notranslate"><span class="pre">safe_sqr</span></code></a>: Helper function for unified squaring (<code class="docutils literal notranslate"><span class="pre">**2</span></code>) of
array-likes, matrices and sparse matrices.</p></li>
</ul>
</section>
<section id="hash-functions">
<h2>Hash Functions<a class="headerlink" href="#hash-functions" title="Permalink to this heading">¶</a></h2>
<ul>
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.murmurhash3_32.html#sklearn.utils.murmurhash3_32" title="sklearn.utils.murmurhash3_32"><code class="xref py py-func docutils literal notranslate"><span class="pre">murmurhash3_32</span></code></a> provides a python wrapper for the
<code class="docutils literal notranslate"><span class="pre">MurmurHash3_x86_32</span></code> C++ non cryptographic hash function. This hash
function is suitable for implementing lookup tables, Bloom filters,
Count Min Sketch, feature hashing and implicitly defined sparse
random projections:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">sklearn.utils</span> <span class="kn">import</span> <span class="n">murmurhash3_32</span>
<span class="gp">>>> </span><span class="n">murmurhash3_32</span><span class="p">(</span><span class="s2">"some feature"</span><span class="p">,</span> <span class="n">seed</span><span class="o">=</span><span class="mi">0</span><span class="p">)</span> <span class="o">==</span> <span class="o">-</span><span class="mi">384616559</span>
<span class="go">True</span>
<span class="gp">>>> </span><span class="n">murmurhash3_32</span><span class="p">(</span><span class="s2">"some feature"</span><span class="p">,</span> <span class="n">seed</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span> <span class="n">positive</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span> <span class="o">==</span> <span class="mi">3910350737</span>
<span class="go">True</span>
</pre></div>
</div>
<p>The <code class="docutils literal notranslate"><span class="pre">sklearn.utils.murmurhash</span></code> module can also be “cimported” from
other cython modules so as to benefit from the high performance of
MurmurHash while skipping the overhead of the Python interpreter.</p>
</li>
</ul>
</section>
<section id="warnings-and-exceptions">
<h2>Warnings and Exceptions<a class="headerlink" href="#warnings-and-exceptions" title="Permalink to this heading">¶</a></h2>
<ul class="simple">
<li><p><a class="reference internal" href="../modules/generated/sklearn.utils.deprecated.html#sklearn.utils.deprecated" title="sklearn.utils.deprecated"><code class="xref py py-class docutils literal notranslate"><span class="pre">deprecated</span></code></a>: Decorator to mark a function or class as deprecated.</p></li>
<li><p><a class="reference internal" href="../modules/generated/sklearn.exceptions.ConvergenceWarning.html#sklearn.exceptions.ConvergenceWarning" title="sklearn.exceptions.ConvergenceWarning"><code class="xref py py-class docutils literal notranslate"><span class="pre">ConvergenceWarning</span></code></a>: Custom warning to catch
convergence problems. Used in <code class="docutils literal notranslate"><span class="pre">sklearn.covariance.graphical_lasso</span></code>.</p></li>
</ul>
</section>
</section>
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