Python supports chained comparison operators like `a < b < c`, evaluating them as `(a < b) and (b < c)` with short-circuit semantics — unlike C, which evaluates left-to-right using the result of each comparison as the next operand. Using Python's `dis` module, the bytecode for chained comparisons is dissected instruction by instruction, revealing how `DUP_TOP` and `ROT_THREE` preserve the middle operand, and how `JUMP_IF_FALSE_OR_POP` implements short-circuiting. The post then walks through modifying CPython's `compiler_compare` function in `compile.c` to remove those three instructions, making Python evaluate chained comparisons the C way — causing `-3 < -2 < -1` to return `False` instead of `True`.
Table of contents
Chaining comparison operatorsChaining under the hoodMake chain evaluation C-likeReferences11 Impressions