[petercorke]

Part of #23.

What

16 assert statements in PGraph.py (Bandit B101) existed only to tell mypy that an optional value was set. Fourteen are now gone:

Was	Now
assert e.v1 is not None and e.v2 is not None (11 places: edge layout, the edge artist, plot(), incidence(), _attach of both graph types, Edge.next, Edge.endpoints)	v1, v2 = e._ends()
assert v.name is not None (3 places: remove_vertex, path_UCS, path_Astar)	v._require_name()

Edge._ends() and Vertex._require_name() return the value or raise ValueError, in the manner of the existing Graph._require_cost(). mypy sees the narrowed type, and the check is real: it is not removed by python -O, which is what B101 warns about.

The two asserts left (the coordinate of a candidate in near(), the graph in Vertex.connect()) are type narrowing too, with no helper that would make them clearer. They are commented as such and marked # nosec B101. I did not exclude B101 for src/, in line with RTB and bdsim, which exclude it only for tests/.

Behaviour

Nothing changes for a connected edge or a named vertex, which is every edge and vertex in a graph. An unconnected Edge() now raises ValueError("the edge is not connected to two vertices") from .endpoints and .next(), where it raised AssertionError (and next() raised ValueError("should not happen")).

Performance

_attach runs for every edge added, so the helper adds a call on that path. Measured against main (git archive main src, three runs each, best of 7 within a run) on 90,000 edges over 30,000 vertices:

	main	this branch
UGraph.add_edge	114.5, 114.9, 115.8 ms	112.8, 113.7, 115.5 ms
DGraph.add_edge	114.6, 116.1, 114.7 ms	114.5, 112.2, 112.6 ms

No difference beyond noise (about 1.3 µs per edge either way). My path_UCS benchmark (0.5 ms) found no path, so it says nothing about the search itself; the change there is only the final loop that builds the parent names.

Tests

• Edge._ends() / endpoints / next() on a connected edge, on an unconnected Edge(), and next() of a vertex that is not an end
• Vertex._require_name() with and without a name

pytest tests: 777 passed. mypy src: clean.

🤖 Generated with Claude Code

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 4 complexity · 0 duplication

Metric	Results
Complexity	4
Duplication	0

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.05%. Comparing base (343a0f2) to head (7adc047).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #88      +/-   ##
==========================================
+ Coverage   97.98%   98.05%   +0.06%     
==========================================
  Files           4        4              
  Lines        1586     1590       +4     
==========================================
+ Hits         1554     1559       +5     
+ Misses         32       31       -1     

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