### view env/lib/python3.9/site-packages/networkx/generators/tests/test_trees.py @ 0:4f3585e2f14bdraftdefaulttip

author shellac Mon, 22 Mar 2021 18:12:50 +0000
line wrap: on
line source
```
import networkx as nx
from networkx.generators.trees import NIL
from networkx.utils import arbitrary_element

class TestPrefixTree:
"""Unit tests for the prefix tree generator function."""

def test_basic(self):
# This example is from the Wikipedia article "Trie"
# <https://en.wikipedia.org/wiki/Trie>.
strings = ["a", "to", "tea", "ted", "ten", "i", "in", "inn"]
T, root = nx.prefix_tree(strings)

def source_label(v):
return T.nodes[v]["source"]

# First, we check that the tree has the expected
# structure. Recall that each node that corresponds to one of
# the input strings has an edge to the NIL node.
#
# Consider the three children at level 1 in the trie.
a, i, t = sorted(T[root], key=source_label)
# Check the 'a' branch.
assert len(T[a]) == 1
nil = arbitrary_element(T[a])
assert len(T[nil]) == 0
# Check the 'i' branch.
assert len(T[i]) == 2
nil, in_ = sorted(T[i], key=source_label)
assert len(T[nil]) == 0
assert len(T[in_]) == 2
nil, inn = sorted(T[in_], key=source_label)
assert len(T[nil]) == 0
assert len(T[inn]) == 1
nil = arbitrary_element(T[inn])
assert len(T[nil]) == 0
# Check the 't' branch.
te, to = sorted(T[t], key=source_label)
assert len(T[to]) == 1
nil = arbitrary_element(T[to])
assert len(T[nil]) == 0
tea, ted, ten = sorted(T[te], key=source_label)
assert len(T[tea]) == 1
assert len(T[ted]) == 1
assert len(T[ten]) == 1
nil = arbitrary_element(T[tea])
assert len(T[nil]) == 0
nil = arbitrary_element(T[ted])
assert len(T[nil]) == 0
nil = arbitrary_element(T[ten])
assert len(T[nil]) == 0

# Next, we check that the "sources" of each of the nodes is the
# rightmost letter in the string corresponding to the path to
# that node.
assert source_label(root) is None
assert source_label(a) == "a"
assert source_label(i) == "i"
assert source_label(t) == "t"
assert source_label(in_) == "n"
assert source_label(inn) == "n"
assert source_label(to) == "o"
assert source_label(te) == "e"
assert source_label(tea) == "a"
assert source_label(ted) == "d"
assert source_label(ten) == "n"
assert source_label(NIL) == NIL

def test_random_tree():
"""Tests that a random tree is in fact a tree."""
T = nx.random_tree(10, seed=1234)
assert nx.is_tree(T)
```