boltons
Extended Python standard library — provides utilities that 'should be in the stdlib' covering iterables, strings, functions, types, caching, time, stats, and more. boltons modules: iterutils (chunked, flatten, pairwise, windowed, first, one, remap), strutils (slugify, strip_ansi, bytes2human, html2text), funcutils (wraps, partial, FunctionBuilder), typeutils (make_sentinel), cacheutils (LRU, LRI, ThresholdCounter), timeutils (relative_time, decimal_time), statsutils (median, trimean, Histogram), ecoutils (get_process_tree), fileutils (atomic_save, mkdir_p), jsonutils (reverse_iter_lines), and tableutils (Table). Zero-dependency pure Python.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Pure utility library with zero dependencies and no network calls. atomic_save uses os.rename() which is atomic on POSIX — safe for concurrent writers. No security concerns beyond standard file permissions.
⚡ Reliability
Best When
Python utility functions that are nearly-stdlib quality — boltons fills gaps in Python standard library (chunked iterables, slugify, atomic saves, LRU cache) with zero dependencies and simple API.
Avoid When
You need high-performance data processing (use numpy/pandas), async utilities, or deep functionality in any one area (use specialized libraries).
Use Cases
- • Agent list chunking — from boltons.iterutils import chunked, windowed, pairwise; chunks = list(chunked(agent_results, 10)); windows = list(windowed(time_series, 3)) — chunked splits into N-sized chunks; windowed slides window over sequence; agent batch processing splits results into chunks for parallel processing; pairwise for consecutive element comparison
- • Agent recursive data transformation — from boltons.iterutils import remap; clean = remap(raw_api_data, lambda p, k, v: v is not None) — remap walks nested structure and rebuilds with filter; agent cleans None values from nested LLM response dict; remap(data, visit=lambda p, k, v: (k, str(v))) converts all values to strings
- • Agent string utilities — from boltons.strutils import slugify, bytes2human, strip_ansi; slug = slugify('Agent Task: Run #1!') — 'agent-task-run-1'; size_str = bytes2human(file_size) — '1.5 GB'; clean_text = strip_ansi(terminal_output) — agent display formatting, file naming, terminal output cleaning in one library
- • Agent bounded LRU cache — from boltons.cacheutils import LRU; cache = LRU(max_size=1000); cache['key'] = value; result = cache.get('key', default) — dict-like LRU with size limit; agent embedding cache with bounded memory; ThreadSafe=True option for concurrent access; LRI for insertion-ordered cache
- • Agent atomic file save — from boltons.fileutils import atomic_save; with atomic_save('/path/to/agent_state.json') as f: json.dump(state, f) — writes to temp file then renames; agent state persistence is crash-safe; partial writes never corrupt state file; atomic_save handles temp file and rename atomically
Not For
- • High-performance data processing — boltons is pure Python; for numerical arrays use numpy; for DataFrames use pandas
- • Async code — boltons is synchronous; async alternatives exist for specific use cases
- • Replacing purpose-built libraries — boltons provides breadth not depth; for advanced caching use cachetools; for advanced itertools use more-itertools
Interface
Authentication
No auth — pure Python utility library with no network calls.
Pricing
boltons is BSD licensed. Free for all use.
Agent Metadata
Known Gotchas
- ⚠ chunked returns lists not generator — from boltons.iterutils import chunked; chunked(range(10), 3) returns list of lists immediately; not lazy; agent processing very large sequences should use chunked_iter for lazy evaluation: from boltons.iterutils import chunked_iter; chunked_iter(large_seq, 1000) yields chunks on demand
- ⚠ LRU cache is not thread-safe by default — boltons.cacheutils.LRU() has no locking; concurrent reads/writes from multiple threads corrupt cache state; agent code using LRU in multithreaded context must use threading.Lock() or use LRU(on_miss=...) with external synchronization; simpler: use functools.lru_cache or cachetools.LRUCache(maxsize=N) with RLock
- ⚠ remap visit function signature is (path, key, value) — remap(data, visit=fn) calls fn(path, key, value); path is tuple of keys from root; agent code with visit=lambda k, v: ... has wrong signature and receives (path, key) as positional args k and v; correct: visit=lambda path, key, value: ...; wrong signature causes subtle bugs where path is treated as filter key
- ⚠ atomic_save requires writable directory — atomic_save('/path/file.json') writes temp file to same directory as target; if directory not writable or on different filesystem, rename fails; agent code saving to read-only dirs or cross-filesystem paths raises OSError; ensure temp and target are on same filesystem (same partition)
- ⚠ strutils.slugify behavior differs from other slug libraries — boltons slugify('Hello World') returns 'hello-world'; handles Unicode by transliterating; for non-ASCII text: slugify('Héllo') returns 'hello' (strips accents); agent internationalization may need custom slugify for non-Latin scripts; boltons slugify works best for ASCII/Latin text
- ⚠ boltons.iterutils.first() returns None not raising — first(empty_list) returns None not StopIteration or KeyError; agent code using first() to get required element must check: result = first(items); if result is None: raise ValueError('expected item'); omitting check silently propagates None downstream
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Scores are editorial opinions as of 2026-03-06.