⚡️ Speed up method Cache.pop by 25%

[codeflash-ai]

📄 25% (0.25x) speedup for Cache.pop in electrum/lrucache.py

⏱️ Runtime : 688 microseconds → 549 microseconds (best of 250 runs)

📝 Explanation and details

The optimization replaces an inefficient double lookup pattern with a more direct try/except approach that eliminates redundant dictionary operations.

Key changes:

• Original approach: Uses if key in self: followed by value = self[key] - this performs two separate lookups in the underlying dictionary for the common case where the key exists
• Optimized approach: Uses try: value = self.__data[key] followed by del self[key] - this performs only one lookup for the happy path

Why this is faster:

1. Eliminates double lookup: The original code checks membership (key in self) then retrieves the value (self[key]), each triggering hash computation and dictionary traversal. The optimized version does a single direct access to self.__data[key].

2. Leverages EAFP principle: Python's "Easier to Ask for Forgiveness than Permission" approach is generally faster than checking conditions first, especially when the expected case (key exists) is common.

3. Reduces method call overhead: Direct access to self.__data[key] avoids the __getitem__ method call indirection.

Performance characteristics:

• Existing keys (most common case): ~25-40% faster due to single lookup
• Missing keys: Slightly slower (~5-18%) due to exception handling overhead, but this is the less common path
• Large caches: Shows consistent 20-35% improvement as the benefits compound with scale

The optimization is particularly effective for cache workloads where cache hits are frequent, making this a worthwhile trade-off that prioritizes the common success case over the exceptional failure case.

✅ Correctness verification report:

Test	Status
⚙️ Existing Unit Tests	🔘 None Found
🌀 Generated Regression Tests	✅ 1504 Passed
⏪ Replay Tests	🔘 None Found
🔎 Concolic Coverage Tests	🔘 None Found
📊 Tests Coverage	100.0%

🌀 Generated Regression Tests and Runtime

import pytest  # used for our unit tests
from electrum.lrucache import Cache

# function to test
# (see above: Cache class with pop method)

# -----------------------
# Unit Tests for Cache.pop
# -----------------------

# ----
# Basic Test Cases
# ----

def test_pop_basic_existing_key():
    # Test popping an existing key
    cache = Cache(10)
    cache['a'] = 1
    cache['b'] = 2
    # Should return the value and remove the key
    codeflash_output = cache.pop('a') # 1.43μs -> 1.13μs (26.1% faster)

def test_pop_basic_non_existing_key_with_default():
    # Test popping a non-existing key with default
    cache = Cache(10)
    cache['x'] = 100
    # Should return default value and not raise
    codeflash_output = cache.pop('y', 999) # 767ns -> 928ns (17.3% slower)

def test_pop_basic_non_existing_key_without_default():
    # Test popping a non-existing key without default (should raise KeyError)
    cache = Cache(10)
    cache['foo'] = 'bar'
    with pytest.raises(KeyError):
        cache.pop('baz') # 1.13μs -> 1.19μs (5.36% slower)

def test_pop_basic_default_is_None():
    # Test popping a non-existing key with default=None
    cache = Cache(10)
    codeflash_output = cache.pop('missing', None) # 768ns -> 853ns (9.96% slower)

def test_pop_basic_default_is_zero():
    # Test popping a non-existing key with default=0
    cache = Cache(10)
    codeflash_output = cache.pop('missing', 0) # 716ns -> 812ns (11.8% slower)

# ----
# Edge Test Cases
# ----

def test_pop_empty_cache():
    # Test popping from an empty cache (should raise KeyError)
    cache = Cache(10)
    with pytest.raises(KeyError):
        cache.pop('anything') # 1.05μs -> 1.14μs (7.63% slower)

def test_pop_empty_cache_with_default():
    # Test popping from an empty cache with default
    cache = Cache(10)
    codeflash_output = cache.pop('anything', 'default') # 722ns -> 834ns (13.4% slower)

def test_pop_key_with_falsy_value():
    # Test popping a key with a falsy value (0, '', False)
    cache = Cache(10)
    cache['zero'] = 0
    cache['empty'] = ''
    cache['false'] = False
    codeflash_output = cache.pop('zero') # 1.57μs -> 1.13μs (38.9% faster)
    codeflash_output = cache.pop('empty') # 793ns -> 578ns (37.2% faster)
    codeflash_output = cache.pop('false') # 631ns -> 399ns (58.1% faster)

def test_pop_key_with_None_value():
    # Test popping a key with value None
    cache = Cache(10)
    cache['none'] = None
    codeflash_output = cache.pop('none') # 1.26μs -> 930ns (35.2% faster)

def test_pop_key_with_mutable_value():
    # Test popping a key with a mutable value (list)
    cache = Cache(10)
    cache['lst'] = [1,2,3]
    codeflash_output = cache.pop('lst'); val = codeflash_output # 1.18μs -> 903ns (30.6% faster)

def test_pop_twice_same_key():
    # Test popping the same key twice (second should raise)
    cache = Cache(10)
    cache['a'] = 123
    codeflash_output = cache.pop('a') # 1.17μs -> 888ns (31.9% faster)
    with pytest.raises(KeyError):
        cache.pop('a') # 908ns -> 1.09μs (16.6% slower)

def test_pop_after_cache_eviction():
    # Test pop after cache evicts items (simulate LRU eviction)
    cache = Cache(2)
    cache['x'] = 1
    cache['y'] = 2
    # Add a third item to force eviction
    cache['z'] = 3
    # Try popping an evicted key
    evicted_key = 'x' if 'x' not in cache else 'y'
    with pytest.raises(KeyError):
        cache.pop(evicted_key) # 1.03μs -> 1.13μs (8.87% slower)

def test_pop_with_non_hashable_key():
    # Test popping with a non-hashable key (should raise TypeError)
    cache = Cache(10)
    with pytest.raises(TypeError):
        cache.pop(['unhashable']) # 1.35μs -> 1.20μs (12.4% faster)

def test_pop_with_integer_keys():
    # Test popping integer keys
    cache = Cache(10)
    cache[1] = 'one'
    cache[2] = 'two'
    codeflash_output = cache.pop(1) # 1.50μs -> 1.10μs (35.4% faster)

def test_pop_with_tuple_keys():
    # Test popping tuple keys
    cache = Cache(10)
    cache[(1,2)] = 'tuple'
    codeflash_output = cache.pop((1,2)) # 1.42μs -> 1.05μs (35.1% faster)

def test_pop_with_custom_object_key():
    # Test popping with a custom object as key
    class MyKey:
        def __hash__(self): return 42
        def __eq__(self, other): return isinstance(other, MyKey)
    key = MyKey()
    cache = Cache(10)
    cache[key] = 'custom'
    codeflash_output = cache.pop(key) # 1.55μs -> 1.19μs (29.5% faster)

def test_pop_with_multiple_types():
    # Test popping keys of multiple types
    cache = Cache(10)
    cache['str'] = 1
    cache[42] = 2
    cache[(1,2)] = 3
    codeflash_output = cache.pop('str') # 1.37μs -> 1.02μs (33.8% faster)
    codeflash_output = cache.pop(42) # 670ns -> 453ns (47.9% faster)
    codeflash_output = cache.pop((1,2)) # 528ns -> 547ns (3.47% slower)

# ----
# Large Scale Test Cases
# ----

def test_pop_large_cache():
    # Test popping from a large cache (up to 1000 items)
    cache = Cache(1000)
    for i in range(1000):
        cache[i] = i * 2
    # Pop a few keys and check correctness
    codeflash_output = cache.pop(0) # 1.37μs -> 1.00μs (36.5% faster)
    codeflash_output = cache.pop(999) # 785ns -> 562ns (39.7% faster)
    codeflash_output = cache.pop(500) # 568ns -> 460ns (23.5% faster)

def test_pop_all_keys_large_cache():
    # Pop all keys one by one from a large cache
    cache = Cache(1000)
    for i in range(1000):
        cache[i] = i
    for i in range(1000):
        codeflash_output = cache.pop(i) # 442μs -> 349μs (26.6% faster)

def test_pop_performance_large_cache():
    # Test that pop is fast for large cache (does not hang)
    cache = Cache(1000)
    for i in range(1000):
        cache[i] = i
    # Pop 100 random keys quickly
    for i in range(0, 1000, 10):
        codeflash_output = cache.pop(i) # 47.0μs -> 36.8μs (27.8% faster)

def test_pop_with_large_values():
    # Test pop with large values and custom getsizeof
    def getsizeof(val): return len(val)
    cache = Cache(1000, getsizeof=getsizeof)
    cache['big'] = 'x' * 500
    cache['bigger'] = 'y' * 499
    codeflash_output = cache.pop('big') # 1.37μs -> 1.02μs (34.0% faster)
    codeflash_output = cache.pop('bigger') # 835ns -> 599ns (39.4% faster)


def test_pop_removes_key():
    # After pop, key must not be in cache
    cache = Cache(10)
    cache['a'] = 1
    cache.pop('a') # 1.35μs -> 923ns (46.3% faster)

def test_pop_returns_value_and_removes_key():
    # pop must return the correct value and remove the key
    cache = Cache(10)
    cache['x'] = 42
    codeflash_output = cache.pop('x'); val = codeflash_output # 1.22μs -> 927ns (31.4% faster)

def test_pop_does_not_remove_other_keys():
    # pop must not remove other keys
    cache = Cache(10)
    cache['a'] = 1
    cache['b'] = 2
    cache.pop('a') # 1.27μs -> 890ns (42.4% faster)

# ----
# pop must raise KeyError for missing key if no default
# ----

def test_pop_raises_keyerror_for_missing_key():
    cache = Cache(10)
    with pytest.raises(KeyError):
        cache.pop('not-there') # 1.13μs -> 1.22μs (7.32% slower)

# ----
# pop must return default for missing key if default provided
# ----

def test_pop_returns_default_for_missing_key():
    cache = Cache(10)
    codeflash_output = cache.pop('not-there', 'default') # 781ns -> 893ns (12.5% slower)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.
#------------------------------------------------
import collections.abc
from typing import TypeVar

# imports
import pytest  # used for our unit tests
from electrum.lrucache import Cache

_KT = TypeVar("_KT")
_VT = TypeVar("_VT")

class _DefaultSize(dict):
    def __getitem__(self, k):
        return 1
from electrum.lrucache import Cache

# unit tests

# --- Basic Test Cases ---

def test_pop_existing_key():
    # Test popping an existing key returns its value and removes it
    cache = Cache(10)
    cache['a'] = 1
    codeflash_output = cache.pop('a') # 1.49μs -> 1.25μs (19.3% faster)

def test_pop_existing_key_with_default():
    # Popping an existing key with a default should ignore the default and return the value
    cache = Cache(10)
    cache['x'] = 42
    codeflash_output = cache.pop('x', 'default') # 1.32μs -> 966ns (36.6% faster)

def test_pop_nonexistent_key_with_default():
    # Popping a missing key with a default should return the default
    cache = Cache(10)
    codeflash_output = cache.pop('missing', 'default') # 763ns -> 847ns (9.92% slower)

def test_pop_nonexistent_key_raises_keyerror():
    # Popping a missing key without default should raise KeyError
    cache = Cache(10)
    with pytest.raises(KeyError):
        cache.pop('missing') # 1.16μs -> 1.22μs (4.92% slower)

def test_pop_removes_key_and_decrements_len():
    # After popping, the key should be gone and length decremented
    cache = Cache(10)
    cache['k'] = 99
    cache.pop('k') # 1.51μs -> 1.14μs (32.9% faster)

def test_pop_multiple_keys():
    # Pop several keys and check values and state
    cache = Cache(10)
    cache['a'] = 1
    cache['b'] = 2
    cache['c'] = 3
    codeflash_output = cache.pop('a') # 1.29μs -> 1.02μs (26.9% faster)
    codeflash_output = cache.pop('b') # 798ns -> 585ns (36.4% faster)
    codeflash_output = cache.pop('c') # 487ns -> 395ns (23.3% faster)

# --- Edge Test Cases ---

def test_pop_with_none_key():
    # Test popping when None is used as a key
    cache = Cache(10)
    cache[None] = 'none-value'
    codeflash_output = cache.pop(None) # 1.27μs -> 921ns (38.2% faster)

def test_pop_with_integer_key():
    # Integer keys should work as expected
    cache = Cache(10)
    cache[123] = 'int-value'
    codeflash_output = cache.pop(123) # 1.34μs -> 964ns (39.5% faster)

def test_pop_with_tuple_key():
    # Tuple keys should work as expected
    cache = Cache(10)
    key = (1, 2, 3)
    cache[key] = 'tuple-value'
    codeflash_output = cache.pop(key) # 1.37μs -> 984ns (39.6% faster)

def test_pop_with_object_key():
    # Arbitrary object as key
    class MyKey: pass
    k = MyKey()
    cache = Cache(10)
    cache[k] = 'object-value'
    codeflash_output = cache.pop(k) # 1.32μs -> 988ns (33.5% faster)

def test_pop_with_falsey_default():
    # Falsey default values should be returned if key is missing
    cache = Cache(10)
    codeflash_output = cache.pop('missing', 0) # 771ns -> 896ns (14.0% slower)
    codeflash_output = cache.pop('missing', '') # 285ns -> 350ns (18.6% slower)
    codeflash_output = cache.pop('missing', False) # 232ns -> 254ns (8.66% slower)

def test_pop_after_deletion():
    # Popping a key after it's been deleted should raise KeyError
    cache = Cache(10)
    cache['x'] = 1
    cache.pop('x') # 1.34μs -> 989ns (35.3% faster)
    with pytest.raises(KeyError):
        cache.pop('x') # 966ns -> 1.11μs (12.9% slower)

def test_pop_on_empty_cache():
    # Popping from an empty cache should raise KeyError
    cache = Cache(10)
    with pytest.raises(KeyError):
        cache.pop('nothing') # 1.12μs -> 1.09μs (2.38% faster)

def test_pop_does_not_affect_other_keys():
    # Popping one key should not affect others
    cache = Cache(10)
    cache['a'] = 1
    cache['b'] = 2
    cache.pop('a') # 1.47μs -> 1.12μs (32.0% faster)

def test_pop_with_mutable_value():
    # Popping a key with a mutable value should return the correct object
    cache = Cache(10)
    val = [1,2,3]
    cache['list'] = val
    codeflash_output = cache.pop('list'); out = codeflash_output # 1.32μs -> 941ns (40.2% faster)

def test_pop_with_custom_getsizeof():
    # Test with custom getsizeof function
    def getsizeof(x): return len(str(x))
    cache = Cache(10, getsizeof=getsizeof)
    cache['a'] = '123'
    codeflash_output = cache.pop('a') # 1.43μs -> 992ns (44.6% faster)

# --- Large Scale Test Cases ---

def test_pop_large_number_of_keys():
    # Pop keys from a cache with many entries
    cache = Cache(1000)
    for i in range(1000):
        cache[i] = i
    # Pop every 10th key
    for i in range(0, 1000, 10):
        codeflash_output = cache.pop(i) # 47.1μs -> 37.5μs (25.7% faster)
    # Check remaining keys
    for i in range(0, 1000, 10):
        pass

def test_pop_all_keys_one_by_one():
    # Pop every key one by one
    cache = Cache(100)
    for i in range(100):
        cache[i] = i * 2
    for i in range(100):
        codeflash_output = cache.pop(i); val = codeflash_output # 43.9μs -> 36.1μs (21.8% faster)

def test_pop_performance_under_load():
    # Ensure pop is efficient and correct under load
    cache = Cache(1000)
    for i in range(1000):
        cache[i] = str(i)
    # Pop first and last key
    codeflash_output = cache.pop(0) # 1.34μs -> 992ns (35.1% faster)
    codeflash_output = cache.pop(999) # 775ns -> 577ns (34.3% faster)

def test_pop_with_large_values_and_custom_getsizeof():
    # Custom getsizeof with large values
    def getsizeof(x): return len(x)
    cache = Cache(1000, getsizeof=getsizeof)
    cache['big'] = 'x' * 500
    cache['bigger'] = 'y' * 499
    codeflash_output = cache.pop('big') # 1.40μs -> 1.02μs (37.5% faster)
    codeflash_output = cache.pop('bigger') # 871ns -> 580ns (50.2% faster)

def test_pop_all_keys_reverse_order():
    # Pop all keys in reverse order
    cache = Cache(100)
    for i in range(100):
        cache[i] = i
    for i in reversed(range(100)):
        codeflash_output = cache.pop(i) # 43.9μs -> 36.3μs (21.2% faster)
# codeflash_output is used to check that the output of the original code is the same as that of the optimized code.

To edit these changes git checkout codeflash/optimize-Cache.pop-mhlhlxku and push.