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<section id="migration-guide-from-1-x-to-2-0">
<h1>Migration guide from 1.X to 2.0<a class="headerlink" href="#migration-guide-from-1-x-to-2-0" title="Permalink to this heading">#</a></h1>
<p>This is a guide for people moving from NetworkX 1.X to NetworkX 2.0</p>
<p>Any issues with these can be discussed on the <a class="reference external" href="https://groups.google.com/forum/#!forum/networkx-discuss">mailing list</a>.</p>
<p>At the bottom of this document we discuss how to create code that will
work with both NetworkX v1.x and v2.0.</p>
<p>We have made some major changes to the methods in the Multi/Di/Graph classes.
The methods changed are explained with examples below.</p>
<p>With the release of NetworkX 2.0 we are moving to a view/iterator reporting API.
We have changed many methods from reporting lists or dicts to iterating over
the information. Most of the changes in this regard are in the base classes.
Methods that used to return containers now return views (inspired from
<a class="reference external" href="https://docs.python.org/3/library/stdtypes.html#dict-views">dictionary views</a>
in Python) and methods that returned an iterator have been removed.
The methods which create new graphs have changed in the depth of data copying.
<code class="docutils literal notranslate"><span class="pre">G.subgraph</span></code>/<code class="docutils literal notranslate"><span class="pre">edge_subgraph</span></code>/<code class="docutils literal notranslate"><span class="pre">reverse</span></code>/<code class="docutils literal notranslate"><span class="pre">to_directed</span></code>/<code class="docutils literal notranslate"><span class="pre">to_undirected</span></code>
are affected. Many now have options for view creation instead of copying data.
The depth of the data copying may have also changed.</p>
<p>One View example is <code class="docutils literal notranslate"><span class="pre">G.nodes</span></code> (or <code class="docutils literal notranslate"><span class="pre">G.nodes()</span></code>) which now returns a
dict-like NodeView while <code class="docutils literal notranslate"><span class="pre">G.nodes_iter()</span></code> has been removed. Similarly
for views with <code class="docutils literal notranslate"><span class="pre">G.edges</span></code> and removing <code class="docutils literal notranslate"><span class="pre">G.edges_iter</span></code>.
The Graph attributes <code class="docutils literal notranslate"><span class="pre">G.node</span></code> and <code class="docutils literal notranslate"><span class="pre">G.edge</span></code> have been removed in favor of
using <code class="docutils literal notranslate"><span class="pre">G.nodes[n]</span></code> and <code class="docutils literal notranslate"><span class="pre">G.edges[u,</span> <span class="pre">v]</span></code>.
Finally, the <code class="docutils literal notranslate"><span class="pre">selfloop</span></code> methods and <code class="docutils literal notranslate"><span class="pre">add_path</span></code>/<code class="docutils literal notranslate"><span class="pre">star</span></code>/<code class="docutils literal notranslate"><span class="pre">cycle</span></code> have
been moved from graph methods to networkx functions.</p>
<p>We expect that these changes will break some code. We have tried to make
them break the code in ways that raise exceptions, so it will be obvious
that code is broken.</p>
<p>There are also a number of improvements to the codebase outside of the base
graph classes. These are too numerous to catalog here, but a couple obvious
ones include:</p>
<ul class="simple">
<li><p>centering of nodes in <code class="docutils literal notranslate"><span class="pre">drawing/nx_pylab</span></code>,</p></li>
<li><p>iterator vs dict output from a few <code class="docutils literal notranslate"><span class="pre">shortest_path</span></code> routines</p></li>
</ul>
<hr class="docutils" />
<p>Some demonstrations:</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">networkx</span> <span class="k">as</span> <span class="nn">nx</span>
<span class="gp">>>> </span><span class="n">G</span> <span class="o">=</span> <span class="n">nx</span><span class="o">.</span><span class="n">complete_graph</span><span class="p">(</span><span class="mi">5</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">G</span><span class="o">.</span><span class="n">nodes</span> <span class="c1"># for backward compatibility G.nodes() works as well</span>
<span class="go">NodeView((0, 1, 2, 3, 4))</span>
</pre></div>
</div>
<p>You can iterate through <code class="docutils literal notranslate"><span class="pre">G.nodes</span></code> (or <code class="docutils literal notranslate"><span class="pre">G.nodes()</span></code>)</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="k">for</span> <span class="n">node</span> <span class="ow">in</span> <span class="n">G</span><span class="o">.</span><span class="n">nodes</span><span class="p">:</span>
<span class="gp">... </span> <span class="nb">print</span><span class="p">(</span><span class="n">node</span><span class="p">)</span>
<span class="go">0</span>
<span class="go">1</span>
<span class="go">2</span>
<span class="go">3</span>
<span class="go">4</span>
</pre></div>
</div>
<p>If you want a list of nodes you can use the Python list function</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">G</span><span class="o">.</span><span class="n">nodes</span><span class="p">)</span>
<span class="go">[0, 1, 2, 3, 4]</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">G.nodes</span></code> is set-like allowing set operations. It is also dict-like in that you
can look up node data with <code class="docutils literal notranslate"><span class="pre">G.nodes[n]['weight']</span></code>. You can still use the calling
interface <code class="docutils literal notranslate"><span class="pre">G.nodes(data='weight')</span></code> to iterate over node/data pairs. In addition
to the dict-like views <code class="docutils literal notranslate"><span class="pre">keys</span></code>/<code class="docutils literal notranslate"><span class="pre">values</span></code>/<code class="docutils literal notranslate"><span class="pre">items</span></code>, <code class="docutils literal notranslate"><span class="pre">G.nodes</span></code> has a data-view
G.nodes.data(‘weight’). The new EdgeView <code class="docutils literal notranslate"><span class="pre">G.edges</span></code> has similar features for edges.</p>
<p>By adding views NetworkX supports some new features like set operations on
views.</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">H</span> <span class="o">=</span> <span class="n">nx</span><span class="o">.</span><span class="n">Graph</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">H</span><span class="o">.</span><span class="n">add_nodes_from</span><span class="p">([</span><span class="mi">1</span><span class="p">,</span> <span class="s1">'networkx'</span><span class="p">,</span> <span class="s1">'2.0'</span><span class="p">])</span>
<span class="gp">>>> </span><span class="n">G</span><span class="o">.</span><span class="n">nodes</span> <span class="o">&</span> <span class="n">H</span><span class="o">.</span><span class="n">nodes</span> <span class="c1"># finding common nodes in 2 graphs</span>
<span class="go">{1}</span>
<span class="gp">>>> </span><span class="c1"># union of nodes in 2 graphs</span>
<span class="gp">>>> </span><span class="n">G</span><span class="o">.</span><span class="n">nodes</span> <span class="o">|</span> <span class="n">H</span><span class="o">.</span><span class="n">nodes</span>
<span class="go">{0, 1, 2, 3, 4, 'networkx', '2.0'}</span>
</pre></div>
</div>
<p>Similarly, <code class="docutils literal notranslate"><span class="pre">G.edges</span></code> now returns an EdgeView instead of a list of edges and it
also supports set operations.</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">G</span><span class="o">.</span><span class="n">edges</span> <span class="c1"># for backward compatibility G.nodes() works as well</span>
<span class="go">EdgeView([(0, 1), (0, 2), (0, 3), (0, 4), (1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)])</span>
<span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">G</span><span class="o">.</span><span class="n">edges</span><span class="p">)</span>
<span class="go">[(0, 1), (0, 2), (0, 3), (0, 4), (1, 2), (1, 3), (1, 4), (2, 3), (2, 4), (3, 4)]</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">G.degree</span></code> now returns a DegreeView. This is less dict-like than the other views
in the sense that it iterates over (node, degree) pairs, does not provide
keys/values/items/get methods. It does provide lookup <code class="docutils literal notranslate"><span class="pre">G.degree[n]</span></code> and
<code class="docutils literal notranslate"><span class="pre">(node,</span> <span class="pre">degree)</span></code> iteration. A dict keyed by nodes to degree values can be
easily created if needed as <code class="docutils literal notranslate"><span class="pre">dict(G.degree)</span></code>.</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">G</span><span class="o">.</span><span class="n">degree</span> <span class="c1"># for backward compatibility G.degree() works as well</span>
<span class="go">DegreeView({0: 4, 1: 4, 2: 4, 3: 4, 4: 4})</span>
<span class="gp">>>> </span><span class="n">G</span><span class="o">.</span><span class="n">degree</span><span class="p">([</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">])</span>
<span class="go">DegreeView({1: 4, 2: 4, 3: 4})</span>
<span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">G</span><span class="o">.</span><span class="n">degree</span><span class="p">([</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">]))</span>
<span class="go">[(1, 4), (2, 4), (3, 4)]</span>
<span class="gp">>>> </span><span class="nb">dict</span><span class="p">(</span><span class="n">G</span><span class="o">.</span><span class="n">degree</span><span class="p">([</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">]))</span>
<span class="go">{1: 4, 2: 4, 3: 4}</span>
<span class="gp">>>> </span><span class="n">G</span><span class="o">.</span><span class="n">degree</span>
<span class="go">DegreeView({0: 4, 1: 4, 2: 4, 3: 4, 4: 4})</span>
<span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">G</span><span class="o">.</span><span class="n">degree</span><span class="p">)</span>
<span class="go">[(0, 4), (1, 4), (2, 4), (3, 4), (4, 4)]</span>
<span class="gp">>>> </span><span class="nb">dict</span><span class="p">(</span><span class="n">G</span><span class="o">.</span><span class="n">degree</span><span class="p">)</span>
<span class="go">{0: 4, 1: 4, 2: 4, 3: 4, 4: 4}</span>
</pre></div>
</div>
<p>The degree of an individual node can be calculated by <code class="docutils literal notranslate"><span class="pre">G.degree[node]</span></code>.
Similar changes have been made to <code class="docutils literal notranslate"><span class="pre">in_degree</span></code> and <code class="docutils literal notranslate"><span class="pre">out_degree</span></code>
for directed graphs. If you want just the degree values, here are some options.
They are shown for <code class="docutils literal notranslate"><span class="pre">in_degree</span></code> of a <code class="docutils literal notranslate"><span class="pre">DiGraph</span></code>, but similar ideas work
for <code class="docutils literal notranslate"><span class="pre">out_degree</span></code> and <code class="docutils literal notranslate"><span class="pre">degree</span></code></p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">DG</span> <span class="o">=</span> <span class="n">nx</span><span class="o">.</span><span class="n">DiGraph</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">DG</span><span class="o">.</span><span class="n">add_weighted_edges_from</span><span class="p">([(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mf">0.5</span><span class="p">),</span> <span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mf">0.75</span><span class="p">)])</span>
<span class="gp">>>> </span><span class="n">deg</span> <span class="o">=</span> <span class="n">DG</span><span class="o">.</span><span class="n">in_degree</span> <span class="c1"># sets up the view</span>
<span class="gp">>>> </span><span class="p">[</span><span class="n">d</span> <span class="k">for</span> <span class="n">n</span><span class="p">,</span> <span class="n">d</span> <span class="ow">in</span> <span class="n">deg</span><span class="p">]</span> <span class="c1"># gets all nodes' degree values</span>
<span class="go">[1, 1, 0]</span>
<span class="gp">>>> </span><span class="p">(</span><span class="n">d</span> <span class="k">for</span> <span class="n">n</span><span class="p">,</span> <span class="n">d</span> <span class="ow">in</span> <span class="n">deg</span><span class="p">)</span> <span class="c1"># iterator over degree values</span>
<span class="go"><generator object <genexpr> ...></span>
<span class="gp">>>> </span><span class="p">[</span><span class="n">deg</span><span class="p">[</span><span class="n">n</span><span class="p">]</span> <span class="k">for</span> <span class="n">n</span> <span class="ow">in</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">3</span><span class="p">]]</span> <span class="c1"># using lookup for only some nodes</span>
<span class="go">[1, 0]</span>
</pre></div>
</div>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="k">for</span> <span class="n">node</span><span class="p">,</span> <span class="n">in_deg</span> <span class="ow">in</span> <span class="nb">dict</span><span class="p">(</span><span class="n">DG</span><span class="o">.</span><span class="n">in_degree</span><span class="p">)</span><span class="o">.</span><span class="n">items</span><span class="p">():</span> <span class="c1"># works for nx1 and nx2</span>
<span class="gp">... </span> <span class="nb">print</span><span class="p">(</span><span class="n">node</span><span class="p">,</span> <span class="n">in_deg</span><span class="p">)</span>
<span class="go">1 1</span>
<span class="go">2 1</span>
<span class="go">3 0</span>
<span class="gp">>>> </span><span class="nb">dict</span><span class="p">(</span><span class="n">DG</span><span class="o">.</span><span class="n">in_degree</span><span class="p">([</span><span class="mi">1</span><span class="p">,</span> <span class="mi">3</span><span class="p">]))</span><span class="o">.</span><span class="n">values</span><span class="p">()</span> <span class="c1"># works for nx1 and nx2</span>
<span class="go">dict_values([1, 0])</span>
<span class="gp">>>> </span><span class="c1"># DG.in_degree(nlist) creates a restricted view for only nodes in nlist.</span>
<span class="gp">>>> </span><span class="c1"># but see the fourth option above for using lookup instead.</span>
<span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">d</span> <span class="k">for</span> <span class="n">n</span><span class="p">,</span> <span class="n">d</span> <span class="ow">in</span> <span class="n">DG</span><span class="o">.</span><span class="n">in_degree</span><span class="p">([</span><span class="mi">1</span><span class="p">,</span> <span class="mi">3</span><span class="p">]))</span>
<span class="go">[1, 0]</span>
</pre></div>
</div>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="p">[</span><span class="nb">len</span><span class="p">(</span><span class="n">nbrs</span><span class="p">)</span> <span class="k">for</span> <span class="n">n</span><span class="p">,</span> <span class="n">nbrs</span> <span class="ow">in</span> <span class="n">DG</span><span class="o">.</span><span class="n">pred</span><span class="o">.</span><span class="n">items</span><span class="p">()]</span> <span class="c1"># probably slightly fastest for all nodes</span>
<span class="go">[1, 1, 0]</span>
<span class="gp">>>> </span><span class="p">[</span><span class="nb">len</span><span class="p">(</span><span class="n">DG</span><span class="o">.</span><span class="n">pred</span><span class="p">[</span><span class="n">n</span><span class="p">])</span> <span class="k">for</span> <span class="n">n</span> <span class="ow">in</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">3</span><span class="p">]]</span> <span class="c1"># probably slightly faster for only some nodes</span>
<span class="go">[1, 0]</span>
</pre></div>
</div>
<hr class="docutils" />
<p>If <code class="docutils literal notranslate"><span class="pre">n</span></code> is a node in <code class="docutils literal notranslate"><span class="pre">G</span></code>, then <code class="docutils literal notranslate"><span class="pre">G.neighbors(n)</span></code> returns an iterator.</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">n</span> <span class="o">=</span> <span class="mi">1</span>
<span class="gp">>>> </span><span class="n">G</span><span class="o">.</span><span class="n">neighbors</span><span class="p">(</span><span class="n">n</span><span class="p">)</span>
<span class="go"><dict_keyiterator object at ...></span>
<span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">G</span><span class="o">.</span><span class="n">neighbors</span><span class="p">(</span><span class="n">n</span><span class="p">))</span>
<span class="go">[0, 2, 3, 4]</span>
</pre></div>
</div>
<p>DiGraphViews behave similar to GraphViews, but have a few more methods.</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">D</span> <span class="o">=</span> <span class="n">nx</span><span class="o">.</span><span class="n">DiGraph</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">D</span><span class="o">.</span><span class="n">add_edges_from</span><span class="p">([(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">),</span> <span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">),</span> <span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">3</span><span class="p">),</span> <span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">4</span><span class="p">)])</span>
<span class="gp">>>> </span><span class="n">D</span><span class="o">.</span><span class="n">nodes</span>
<span class="go">NodeView((1, 2, 3, 4))</span>
<span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">D</span><span class="o">.</span><span class="n">nodes</span><span class="p">)</span>
<span class="go">[1, 2, 3, 4]</span>
<span class="gp">>>> </span><span class="n">D</span><span class="o">.</span><span class="n">edges</span>
<span class="go">OutEdgeView([(1, 2), (1, 3), (2, 3), (2, 4)])</span>
<span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">D</span><span class="o">.</span><span class="n">edges</span><span class="p">)</span>
<span class="go">[(1, 2), (1, 3), (2, 3), (2, 4)]</span>
<span class="gp">>>> </span><span class="n">D</span><span class="o">.</span><span class="n">in_degree</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span>
<span class="go">1</span>
<span class="gp">>>> </span><span class="n">D</span><span class="o">.</span><span class="n">out_degree</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span>
<span class="go">2</span>
<span class="gp">>>> </span><span class="n">D</span><span class="o">.</span><span class="n">in_edges</span>
<span class="go">InEdgeView([(1, 2), (2, 3), (1, 3), (2, 4)])</span>
<span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">D</span><span class="o">.</span><span class="n">in_edges</span><span class="p">())</span>
<span class="go">[(1, 2), (2, 3), (1, 3), (2, 4)]</span>
<span class="gp">>>> </span><span class="n">D</span><span class="o">.</span><span class="n">out_edges</span><span class="p">(</span><span class="mi">2</span><span class="p">)</span>
<span class="go">OutEdgeDataView([(2, 3), (2, 4)])</span>
<span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">D</span><span class="o">.</span><span class="n">out_edges</span><span class="p">(</span><span class="mi">2</span><span class="p">))</span>
<span class="go">[(2, 3), (2, 4)]</span>
<span class="gp">>>> </span><span class="n">D</span><span class="o">.</span><span class="n">in_degree</span>
<span class="go">InDegreeView({1: 0, 2: 1, 3: 2, 4: 1})</span>
<span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">D</span><span class="o">.</span><span class="n">in_degree</span><span class="p">)</span>
<span class="go">[(1, 0), (2, 1), (3, 2), (4, 1)]</span>
<span class="gp">>>> </span><span class="n">D</span><span class="o">.</span><span class="n">successors</span><span class="p">(</span><span class="mi">2</span><span class="p">)</span>
<span class="go"><dict_keyiterator object at ...></span>
<span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">D</span><span class="o">.</span><span class="n">successors</span><span class="p">(</span><span class="mi">2</span><span class="p">))</span>
<span class="go">[3, 4]</span>
<span class="gp">>>> </span><span class="n">D</span><span class="o">.</span><span class="n">predecessors</span><span class="p">(</span><span class="mi">2</span><span class="p">)</span>
<span class="go"><dict_keyiterator object at ...></span>
<span class="gp">>>> </span><span class="nb">list</span><span class="p">(</span><span class="n">D</span><span class="o">.</span><span class="n">predecessors</span><span class="p">(</span><span class="mi">2</span><span class="p">))</span>
<span class="go">[1]</span>
</pre></div>
</div>
<p>The same changes apply to MultiGraphs and MultiDiGraphs.</p>
<hr class="docutils" />
<p>The order of arguments to <code class="docutils literal notranslate"><span class="pre">set_edge_attributes</span></code> and <code class="docutils literal notranslate"><span class="pre">set_node_attributes</span></code> has
changed. The position of <code class="docutils literal notranslate"><span class="pre">name</span></code> and <code class="docutils literal notranslate"><span class="pre">values</span></code> has been swapped, and <code class="docutils literal notranslate"><span class="pre">name</span></code> now
defaults to <code class="docutils literal notranslate"><span class="pre">None</span></code>. The previous call signature of <code class="docutils literal notranslate"><span class="pre">(graph,</span> <span class="pre">name,</span> <span class="pre">value)</span></code> has
been changed to <code class="docutils literal notranslate"><span class="pre">(graph,</span> <span class="pre">value,</span> <span class="pre">name=None)</span></code>. The new style allows for <code class="docutils literal notranslate"><span class="pre">name</span></code> to
be omitted in favor of passing a dictionary of dictionaries to <code class="docutils literal notranslate"><span class="pre">values</span></code>.</p>
<p>A simple method for migrating existing code to the new version is to explicitly
specify the keyword argument names. This method is backwards compatible and
ensures the correct arguments are passed, regardless of the order. For example the old code</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">G</span> <span class="o">=</span> <span class="n">nx</span><span class="o">.</span><span class="n">Graph</span><span class="p">([(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">),</span> <span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">3</span><span class="p">)])</span>
<span class="gp">>>> </span><span class="n">nx</span><span class="o">.</span><span class="n">set_node_attributes</span><span class="p">(</span><span class="n">G</span><span class="p">,</span> <span class="s1">'label'</span><span class="p">,</span> <span class="p">{</span><span class="mi">1</span><span class="p">:</span> <span class="s1">'one'</span><span class="p">,</span> <span class="mi">2</span><span class="p">:</span> <span class="s1">'two'</span><span class="p">,</span> <span class="mi">3</span><span class="p">:</span> <span class="s1">'three'</span><span class="p">})</span>
<span class="gp">>>> </span><span class="n">nx</span><span class="o">.</span><span class="n">set_edge_attributes</span><span class="p">(</span><span class="n">G</span><span class="p">,</span> <span class="s1">'label'</span><span class="p">,</span> <span class="p">{(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">):</span> <span class="s1">'path1'</span><span class="p">,</span> <span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">):</span> <span class="s1">'path2'</span><span class="p">})</span>
</pre></div>
</div>
<p>Will cause <code class="docutils literal notranslate"><span class="pre">TypeError:</span> <span class="pre">unhashable</span> <span class="pre">type:</span> <span class="pre">'dict'</span></code> in the new version. The code
can be refactored as</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">G</span> <span class="o">=</span> <span class="n">nx</span><span class="o">.</span><span class="n">Graph</span><span class="p">([(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">),</span> <span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">3</span><span class="p">)])</span>
<span class="gp">>>> </span><span class="n">nx</span><span class="o">.</span><span class="n">set_node_attributes</span><span class="p">(</span><span class="n">G</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="s1">'label'</span><span class="p">,</span> <span class="n">values</span><span class="o">=</span><span class="p">{</span><span class="mi">1</span><span class="p">:</span> <span class="s1">'one'</span><span class="p">,</span> <span class="mi">2</span><span class="p">:</span> <span class="s1">'two'</span><span class="p">,</span> <span class="mi">3</span><span class="p">:</span> <span class="s1">'three'</span><span class="p">})</span>
<span class="gp">>>> </span><span class="n">nx</span><span class="o">.</span><span class="n">set_edge_attributes</span><span class="p">(</span><span class="n">G</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="s1">'label'</span><span class="p">,</span> <span class="n">values</span><span class="o">=</span><span class="p">{(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">):</span> <span class="s1">'path1'</span><span class="p">,</span> <span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">):</span> <span class="s1">'path2'</span><span class="p">})</span>
</pre></div>
</div>
<hr class="docutils" />
<p>Some methods have been moved from the base graph class into the main namespace.
These are: <code class="docutils literal notranslate"><span class="pre">G.add_path</span></code>, <code class="docutils literal notranslate"><span class="pre">G.add_star</span></code>, <code class="docutils literal notranslate"><span class="pre">G.add_cycle</span></code>, <code class="docutils literal notranslate"><span class="pre">G.number_of_selfloops</span></code>,
<code class="docutils literal notranslate"><span class="pre">G.nodes_with_selfloops</span></code>, and <code class="docutils literal notranslate"><span class="pre">G.selfloop_edges</span></code>.
They are replaced by <code class="docutils literal notranslate"><span class="pre">nx.path_graph(G,</span> <span class="pre">...)</span></code> <code class="docutils literal notranslate"><span class="pre">nx.add_star(G,</span> <span class="pre">...)</span></code>,
<code class="docutils literal notranslate"><span class="pre">nx.selfloop_edges(G)</span></code>, etc.
For backward compatibility, we are leaving them as deprecated methods.</p>
<hr class="docutils" />
<p>With the new GraphViews (SubGraph, ReversedGraph, etc) you can’t assume that
<code class="docutils literal notranslate"><span class="pre">G.__class__()</span></code> will create a new instance of the same graph type as <code class="docutils literal notranslate"><span class="pre">G</span></code>.
In fact, the call signature for <code class="docutils literal notranslate"><span class="pre">__class__</span></code> differs depending on whether <code class="docutils literal notranslate"><span class="pre">G</span></code>
is a view or a base class. For v2.x you should use <code class="docutils literal notranslate"><span class="pre">G.fresh_copy()</span></code> to
create a null graph of the correct type—ready to fill with nodes and edges.</p>
<p>Graph views can also be views-of-views-of-views-of-graphs. If you want to find the
original graph at the end of this chain use <code class="docutils literal notranslate"><span class="pre">G.root_graph</span></code>. Be careful though
because it may be a different graph type (directed/undirected) than the view.</p>
<hr class="docutils" />
<p><code class="docutils literal notranslate"><span class="pre">topological_sort</span></code> no longer accepts <code class="docutils literal notranslate"><span class="pre">reverse</span></code> or <code class="docutils literal notranslate"><span class="pre">nbunch</span></code> arguments.
If <code class="docutils literal notranslate"><span class="pre">nbunch</span></code> was a single node source, then the same effect can now be achieved
using the <code class="docutils literal notranslate"><span class="pre">subgraph</span></code> operator:</p>
<blockquote>
<div><p>nx.topological_sort(G.subgraph(nx.descendants(G, nbunch)))</p>
</div></blockquote>
<p>To achieve a reverse topological sort, the output should be converted to a list:</p>
<blockquote>
<div><p>reversed(list(nx.topological_sort(G)))</p>
</div></blockquote>
<hr class="docutils" />
<section id="writing-code-that-works-for-both-versions">
<h2>Writing code that works for both versions<a class="headerlink" href="#writing-code-that-works-for-both-versions" title="Permalink to this heading">#</a></h2>
<p>Methods <code class="docutils literal notranslate"><span class="pre">set_node_attributes</span></code>/<code class="docutils literal notranslate"><span class="pre">get_node_attributes</span></code>/<code class="docutils literal notranslate"><span class="pre">set_edge_attributes</span></code>/<code class="docutils literal notranslate"><span class="pre">get_edge_attributes</span></code>
have changed the order of their keyword arguments <code class="docutils literal notranslate"><span class="pre">name</span></code> and <code class="docutils literal notranslate"><span class="pre">values</span></code>. So, to make it
work with both versions you should use the keywords in your call.</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">nx</span><span class="o">.</span><span class="n">set_node_attributes</span><span class="p">(</span><span class="n">G</span><span class="p">,</span> <span class="n">values</span><span class="o">=</span><span class="mf">1.0</span><span class="p">,</span> <span class="n">name</span><span class="o">=</span><span class="s1">'weight'</span><span class="p">)</span>
</pre></div>
</div>
<hr class="docutils" />
<p>Change any method with <code class="docutils literal notranslate"><span class="pre">_iter</span></code> in its name to the version without <code class="docutils literal notranslate"><span class="pre">_iter</span></code>.
In v1 this replaces an iterator by a list, but the code will still work.
In v2 this creates a view (which acts like an iterator).</p>
<hr class="docutils" />
<p>Replace any use of <code class="docutils literal notranslate"><span class="pre">G.edge</span></code> with <code class="docutils literal notranslate"><span class="pre">G.adj</span></code>. The Graph attribute <code class="docutils literal notranslate"><span class="pre">edge</span></code>
has been removed. The attribute <code class="docutils literal notranslate"><span class="pre">G.adj</span></code> is <code class="docutils literal notranslate"><span class="pre">G.edge</span></code> in v1 and will work
with both versions.</p>
<hr class="docutils" />
<p>If you use <code class="docutils literal notranslate"><span class="pre">G.node.items()</span></code> or similar in v1.x, you can replace it with
<code class="docutils literal notranslate"><span class="pre">G.nodes(data=True)</span></code> which works for v2.x and v1.x. Iterating over <code class="docutils literal notranslate"><span class="pre">G.node`</span></code>
as in <code class="docutils literal notranslate"><span class="pre">for</span> <span class="pre">n</span> <span class="pre">in</span> <span class="pre">G.node:</span></code> can be replaced with <code class="docutils literal notranslate"><span class="pre">G</span></code>, as in: <code class="docutils literal notranslate"><span class="pre">for</span> <span class="pre">n</span> <span class="pre">in</span> <span class="pre">G:</span></code>.</p>
<hr class="docutils" />
<p>The Graph attribute <code class="docutils literal notranslate"><span class="pre">node</span></code> has moved its functionality to <code class="docutils literal notranslate"><span class="pre">G.nodes</span></code>, so code
expected to work with v2.x should use <code class="docutils literal notranslate"><span class="pre">G.nodes</span></code>.
In fact most uses of <code class="docutils literal notranslate"><span class="pre">G.node</span></code> can be replaced by an idiom that works for both
versions. The functionality that can’t easily is: <code class="docutils literal notranslate"><span class="pre">G.node[n]</span></code>.
In v2.x that becomes <code class="docutils literal notranslate"><span class="pre">G.nodes[n]</span></code> which doesn’t work in v1.x.</p>
<p>Luckily you can still use <code class="docutils literal notranslate"><span class="pre">G.node[n]</span></code> in v2.x when you want it to be able to work
with v1.x too. We have left <code class="docutils literal notranslate"><span class="pre">G.node</span></code> in v2.x as a transition pointer to <code class="docutils literal notranslate"><span class="pre">G.nodes</span></code>.
We envision removing <code class="docutils literal notranslate"><span class="pre">G.node</span></code> in v3.x (sometime in the future).</p>
<hr class="docutils" />
<p>Copying node attribute dicts directly from one graph to another can corrupt
the node data structure if not done correctly. Code such as the following:</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="c1"># dangerous in v1.x, not allowed in v2.x</span>
<span class="gp">>>> </span><span class="n">G</span><span class="o">.</span><span class="n">node</span><span class="p">[</span><span class="n">n</span><span class="p">]</span> <span class="o">=</span> <span class="n">H</span><span class="o">.</span><span class="n">node</span><span class="p">[</span><span class="n">n</span><span class="p">]</span>
</pre></div>
</div>
<p>used to work, even though it could cause errors if <code class="docutils literal notranslate"><span class="pre">n</span></code> was not a node in <code class="docutils literal notranslate"><span class="pre">G</span></code>.
That code will cause an error in v2.x. Replace it with one of the more safe versions:</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="n">G</span><span class="o">.</span><span class="n">nodes</span><span class="p">[</span><span class="n">n</span><span class="p">]</span><span class="o">.</span><span class="n">update</span><span class="p">(</span><span class="n">H</span><span class="o">.</span><span class="n">nodes</span><span class="p">[</span><span class="n">n</span><span class="p">])</span> <span class="c1"># works in v2.x</span>
</pre></div>
</div>
<hr class="docutils" />
<p>The methods removed from the graph classes and put into the main package namespace
can be used via the associated deprecated methods. If you want to update your code
to the new functions, one hack to make that work with both versions is to write
your code for v2.x and add code to the v1 namespace in an ad hoc manner:</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="k">if</span> <span class="n">nx</span><span class="o">.</span><span class="n">__version__</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">==</span> <span class="s1">'1'</span><span class="p">:</span>
<span class="gp">... </span> <span class="n">nx</span><span class="o">.</span><span class="n">add_path</span> <span class="o">=</span> <span class="k">lambda</span> <span class="n">G</span><span class="p">,</span> <span class="n">nodes</span><span class="p">:</span> <span class="n">G</span><span class="o">.</span><span class="n">add_path</span><span class="p">(</span><span class="n">nodes</span><span class="p">)</span>
</pre></div>
</div>
<p>Similarly, v2.x code that uses <code class="docutils literal notranslate"><span class="pre">G.fresh_copy()</span></code> or <code class="docutils literal notranslate"><span class="pre">G.root_graph</span></code> is hard to make
work for v1.x. It may be best in this case to determine the graph type you want
explicitly and call Graph/DiGraph/MultiGraph/MultiDiGraph directly.</p>
</section>
<section id="using-pickle-with-v1-and-v2">
<h2>Using Pickle with v1 and v2<a class="headerlink" href="#using-pickle-with-v1-and-v2" title="Permalink to this heading">#</a></h2>
<p>The Pickle protocol does not store class methods, only the data. So if you write a
pickle file with v1 you should not expect to read it into a v2 Graph. If this happens
to you, read it in with v1 installed and write a file with the node and edge
information. You can read that into a config with v2 installed and then add those nodes
and edges to a fresh graph. Try something similar to this:</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">>>> </span><span class="c1"># in v1.x</span>
<span class="gp">>>> </span><span class="n">pickle</span><span class="o">.</span><span class="n">dump</span><span class="p">([</span><span class="n">G</span><span class="o">.</span><span class="n">nodes</span><span class="p">(</span><span class="n">data</span><span class="o">=</span><span class="kc">True</span><span class="p">),</span> <span class="n">G</span><span class="o">.</span><span class="n">edges</span><span class="p">(</span><span class="n">data</span><span class="o">=</span><span class="kc">True</span><span class="p">)],</span> <span class="n">file</span><span class="p">)</span>
<span class="gp">>>> </span><span class="c1"># then in v2.x</span>
<span class="gp">>>> </span><span class="n">nodes</span><span class="p">,</span> <span class="n">edges</span> <span class="o">=</span> <span class="n">pickle</span><span class="o">.</span><span class="n">load</span><span class="p">(</span><span class="n">file</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">G</span> <span class="o">=</span> <span class="n">nx</span><span class="o">.</span><span class="n">Graph</span><span class="p">()</span>
<span class="gp">>>> </span><span class="n">G</span><span class="o">.</span><span class="n">add_nodes_from</span><span class="p">(</span><span class="n">nodes</span><span class="p">)</span>
<span class="gp">>>> </span><span class="n">G</span><span class="o">.</span><span class="n">add_edges_from</span><span class="p">(</span><span class="n">edges</span><span class="p">)</span>
</pre></div>
</div>
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