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Diffstat (limited to '.venv/lib/python3.12/site-packages/networkx/readwrite/graph6.py')
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1 files changed, 417 insertions, 0 deletions
diff --git a/.venv/lib/python3.12/site-packages/networkx/readwrite/graph6.py b/.venv/lib/python3.12/site-packages/networkx/readwrite/graph6.py new file mode 100644 index 00000000..4ff2f93c --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/readwrite/graph6.py @@ -0,0 +1,417 @@ +# Original author: D. Eppstein, UC Irvine, August 12, 2003. +# The original code at http://www.ics.uci.edu/~eppstein/PADS/ is public domain. +"""Functions for reading and writing graphs in the *graph6* format. + +The *graph6* file format is suitable for small graphs or large dense +graphs. For large sparse graphs, use the *sparse6* format. + +For more information, see the `graph6`_ homepage. + +.. _graph6: http://users.cecs.anu.edu.au/~bdm/data/formats.html + +""" + +from itertools import islice + +import networkx as nx +from networkx.exception import NetworkXError +from networkx.utils import not_implemented_for, open_file + +__all__ = ["from_graph6_bytes", "read_graph6", "to_graph6_bytes", "write_graph6"] + + +def _generate_graph6_bytes(G, nodes, header): + """Yield bytes in the graph6 encoding of a graph. + + `G` is an undirected simple graph. `nodes` is the list of nodes for + which the node-induced subgraph will be encoded; if `nodes` is the + list of all nodes in the graph, the entire graph will be + encoded. `header` is a Boolean that specifies whether to generate + the header ``b'>>graph6<<'`` before the remaining data. + + This function generates `bytes` objects in the following order: + + 1. the header (if requested), + 2. the encoding of the number of nodes, + 3. each character, one-at-a-time, in the encoding of the requested + node-induced subgraph, + 4. a newline character. + + This function raises :exc:`ValueError` if the graph is too large for + the graph6 format (that is, greater than ``2 ** 36`` nodes). + + """ + n = len(G) + if n >= 2**36: + raise ValueError( + "graph6 is only defined if number of nodes is less than 2 ** 36" + ) + if header: + yield b">>graph6<<" + for d in n_to_data(n): + yield str.encode(chr(d + 63)) + # This generates the same as `(v in G[u] for u, v in combinations(G, 2))`, + # but in "column-major" order instead of "row-major" order. + bits = (nodes[j] in G[nodes[i]] for j in range(1, n) for i in range(j)) + chunk = list(islice(bits, 6)) + while chunk: + d = sum(b << 5 - i for i, b in enumerate(chunk)) + yield str.encode(chr(d + 63)) + chunk = list(islice(bits, 6)) + yield b"\n" + + +@nx._dispatchable(graphs=None, returns_graph=True) +def from_graph6_bytes(bytes_in): + """Read a simple undirected graph in graph6 format from bytes. + + Parameters + ---------- + bytes_in : bytes + Data in graph6 format, without a trailing newline. + + Returns + ------- + G : Graph + + Raises + ------ + NetworkXError + If bytes_in is unable to be parsed in graph6 format + + ValueError + If any character ``c`` in bytes_in does not satisfy + ``63 <= ord(c) < 127``. + + Examples + -------- + >>> G = nx.from_graph6_bytes(b"A_") + >>> sorted(G.edges()) + [(0, 1)] + + See Also + -------- + read_graph6, write_graph6 + + References + ---------- + .. [1] Graph6 specification + <http://users.cecs.anu.edu.au/~bdm/data/formats.html> + + """ + + def bits(): + """Returns sequence of individual bits from 6-bit-per-value + list of data values.""" + for d in data: + for i in [5, 4, 3, 2, 1, 0]: + yield (d >> i) & 1 + + if bytes_in.startswith(b">>graph6<<"): + bytes_in = bytes_in[10:] + + data = [c - 63 for c in bytes_in] + if any(c > 63 for c in data): + raise ValueError("each input character must be in range(63, 127)") + + n, data = data_to_n(data) + nd = (n * (n - 1) // 2 + 5) // 6 + if len(data) != nd: + raise NetworkXError( + f"Expected {n * (n - 1) // 2} bits but got {len(data) * 6} in graph6" + ) + + G = nx.Graph() + G.add_nodes_from(range(n)) + for (i, j), b in zip(((i, j) for j in range(1, n) for i in range(j)), bits()): + if b: + G.add_edge(i, j) + + return G + + +@not_implemented_for("directed") +@not_implemented_for("multigraph") +def to_graph6_bytes(G, nodes=None, header=True): + """Convert a simple undirected graph to bytes in graph6 format. + + Parameters + ---------- + G : Graph (undirected) + + nodes: list or iterable + Nodes are labeled 0...n-1 in the order provided. If None the ordering + given by ``G.nodes()`` is used. + + header: bool + If True add '>>graph6<<' bytes to head of data. + + Raises + ------ + NetworkXNotImplemented + If the graph is directed or is a multigraph. + + ValueError + If the graph has at least ``2 ** 36`` nodes; the graph6 format + is only defined for graphs of order less than ``2 ** 36``. + + Examples + -------- + >>> nx.to_graph6_bytes(nx.path_graph(2)) + b'>>graph6<<A_\\n' + + See Also + -------- + from_graph6_bytes, read_graph6, write_graph6_bytes + + Notes + ----- + The returned bytes end with a newline character. + + The format does not support edge or node labels, parallel edges or + self loops. If self loops are present they are silently ignored. + + References + ---------- + .. [1] Graph6 specification + <http://users.cecs.anu.edu.au/~bdm/data/formats.html> + + """ + if nodes is not None: + G = G.subgraph(nodes) + H = nx.convert_node_labels_to_integers(G) + nodes = sorted(H.nodes()) + return b"".join(_generate_graph6_bytes(H, nodes, header)) + + +@open_file(0, mode="rb") +@nx._dispatchable(graphs=None, returns_graph=True) +def read_graph6(path): + """Read simple undirected graphs in graph6 format from path. + + Parameters + ---------- + path : file or string + File or filename to write. + + Returns + ------- + G : Graph or list of Graphs + If the file contains multiple lines then a list of graphs is returned + + Raises + ------ + NetworkXError + If the string is unable to be parsed in graph6 format + + Examples + -------- + You can read a graph6 file by giving the path to the file:: + + >>> import tempfile + >>> with tempfile.NamedTemporaryFile(delete=False) as f: + ... _ = f.write(b">>graph6<<A_\\n") + ... _ = f.seek(0) + ... G = nx.read_graph6(f.name) + >>> list(G.edges()) + [(0, 1)] + + You can also read a graph6 file by giving an open file-like object:: + + >>> import tempfile + >>> with tempfile.NamedTemporaryFile() as f: + ... _ = f.write(b">>graph6<<A_\\n") + ... _ = f.seek(0) + ... G = nx.read_graph6(f) + >>> list(G.edges()) + [(0, 1)] + + See Also + -------- + from_graph6_bytes, write_graph6 + + References + ---------- + .. [1] Graph6 specification + <http://users.cecs.anu.edu.au/~bdm/data/formats.html> + + """ + glist = [] + for line in path: + line = line.strip() + if not len(line): + continue + glist.append(from_graph6_bytes(line)) + if len(glist) == 1: + return glist[0] + else: + return glist + + +@not_implemented_for("directed") +@not_implemented_for("multigraph") +@open_file(1, mode="wb") +def write_graph6(G, path, nodes=None, header=True): + """Write a simple undirected graph to a path in graph6 format. + + Parameters + ---------- + G : Graph (undirected) + + path : str + The path naming the file to which to write the graph. + + nodes: list or iterable + Nodes are labeled 0...n-1 in the order provided. If None the ordering + given by ``G.nodes()`` is used. + + header: bool + If True add '>>graph6<<' string to head of data + + Raises + ------ + NetworkXNotImplemented + If the graph is directed or is a multigraph. + + ValueError + If the graph has at least ``2 ** 36`` nodes; the graph6 format + is only defined for graphs of order less than ``2 ** 36``. + + Examples + -------- + You can write a graph6 file by giving the path to a file:: + + >>> import tempfile + >>> with tempfile.NamedTemporaryFile(delete=False) as f: + ... nx.write_graph6(nx.path_graph(2), f.name) + ... _ = f.seek(0) + ... print(f.read()) + b'>>graph6<<A_\\n' + + See Also + -------- + from_graph6_bytes, read_graph6 + + Notes + ----- + The function writes a newline character after writing the encoding + of the graph. + + The format does not support edge or node labels, parallel edges or + self loops. If self loops are present they are silently ignored. + + References + ---------- + .. [1] Graph6 specification + <http://users.cecs.anu.edu.au/~bdm/data/formats.html> + + """ + return write_graph6_file(G, path, nodes=nodes, header=header) + + +@not_implemented_for("directed") +@not_implemented_for("multigraph") +def write_graph6_file(G, f, nodes=None, header=True): + """Write a simple undirected graph to a file-like object in graph6 format. + + Parameters + ---------- + G : Graph (undirected) + + f : file-like object + The file to write. + + nodes: list or iterable + Nodes are labeled 0...n-1 in the order provided. If None the ordering + given by ``G.nodes()`` is used. + + header: bool + If True add '>>graph6<<' string to head of data + + Raises + ------ + NetworkXNotImplemented + If the graph is directed or is a multigraph. + + ValueError + If the graph has at least ``2 ** 36`` nodes; the graph6 format + is only defined for graphs of order less than ``2 ** 36``. + + Examples + -------- + You can write a graph6 file by giving an open file-like object:: + + >>> import tempfile + >>> with tempfile.NamedTemporaryFile() as f: + ... nx.write_graph6(nx.path_graph(2), f) + ... _ = f.seek(0) + ... print(f.read()) + b'>>graph6<<A_\\n' + + See Also + -------- + from_graph6_bytes, read_graph6 + + Notes + ----- + The function writes a newline character after writing the encoding + of the graph. + + The format does not support edge or node labels, parallel edges or + self loops. If self loops are present they are silently ignored. + + References + ---------- + .. [1] Graph6 specification + <http://users.cecs.anu.edu.au/~bdm/data/formats.html> + + """ + if nodes is not None: + G = G.subgraph(nodes) + H = nx.convert_node_labels_to_integers(G) + nodes = sorted(H.nodes()) + for b in _generate_graph6_bytes(H, nodes, header): + f.write(b) + + +def data_to_n(data): + """Read initial one-, four- or eight-unit value from graph6 + integer sequence. + + Return (value, rest of seq.)""" + if data[0] <= 62: + return data[0], data[1:] + if data[1] <= 62: + return (data[1] << 12) + (data[2] << 6) + data[3], data[4:] + return ( + (data[2] << 30) + + (data[3] << 24) + + (data[4] << 18) + + (data[5] << 12) + + (data[6] << 6) + + data[7], + data[8:], + ) + + +def n_to_data(n): + """Convert an integer to one-, four- or eight-unit graph6 sequence. + + This function is undefined if `n` is not in ``range(2 ** 36)``. + + """ + if n <= 62: + return [n] + elif n <= 258047: + return [63, (n >> 12) & 0x3F, (n >> 6) & 0x3F, n & 0x3F] + else: # if n <= 68719476735: + return [ + 63, + 63, + (n >> 30) & 0x3F, + (n >> 24) & 0x3F, + (n >> 18) & 0x3F, + (n >> 12) & 0x3F, + (n >> 6) & 0x3F, + n & 0x3F, + ] |