Rich Optimization — Lessons Learned

Full case study: rich_org

Context

pip vendors Rich for progress bars, logging, and error display. from rich.console import Console took 79ms on CPython 3.12 — a significant chunk of pip's startup.

What we did

Import deferral (PR #12 + #13)

Deferred 15+ imports across Rich's codebase. The pattern:

# Before (module level)
import re
RE_COLOR = re.compile(r"...")

# After (lazy)
_RE_COLOR = None

def parse(color):
    global _RE_COLOR
    if _RE_COLOR is None:
        import re
        _RE_COLOR = re.compile(r"...")

Key insight: Most regex patterns in Rich are behind LRU-cached methods, so the lazy compile cost is paid once and amortized.

Architectural changes (PR #12)

@dataclass → __slots__: ConsoleOptions and ConsoleThreadLocals used @dataclass, pulling in inspect (~10ms). Replaced with plain classes + __slots__. Memory: 344 → 136 bytes per instance.
Lazy emoji dict: _emoji_codes.EMOJI (3,608 entries) loaded unconditionally. Deferred to first use via module-level __getattr__.

Runtime micro-optimizations (PR #13)

Style.__eq__ identity shortcut: is before hash comparison (1.84x for identity case)
Style.combine/chain: direct _add (LRU-cached) instead of sum() → __add__ (1.34x)
Segment.simplify: is before == for style comparison (1.36x)

Results

Import	Before	After	Speedup
Console (3.12)	79.1ms	37.5ms	2.11x
Console (3.13)	67.9ms	33.6ms	2.02x
RichHandler (3.12)	100.3ms	39.6ms	2.53x

Key takeaways

Python version matters: typing imports re on 3.12 but not 3.13 — this made our re deferral a no-op on 3.12
from __future__ import annotations is the unlock for TYPE_CHECKING moves — without it, annotation-only names that share import lines with runtime names can't be separated
Benchmark on controlled hardware: Laptop results were noisy; Azure non-burstable VM gave consistent ±0.5ms stddev
Maintainer engagement matters: Direct Discord DM to Will McGugan got "Seems like a clear win. Feel free to open a PR" within 30 minutes
Stack PRs, not scatter: Started with 11 individual PRs, consolidated to 2 stacked PRs — much cleaner to review

Applicable to codeflash

Any Rich imports in codeflash's output/display layer are candidates for the same deferral
If codeflash vendors or depends on Rich, the upstream improvements benefit automatically
The @dataclass → __slots__ pattern applies to any hot dataclass in codeflash
Identity shortcut pattern (is before ==) applies to any cached/interned objects

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