functools: Add an implementation for lru_cache.

python-stdlib/functools/README.md

@@ -0,0 +1,11 @@
+# functools
+
+In CPython, `@functools.lru_cache` would also record the *order* of the keyword
+arguments as they are passed to the function to cache the output for.  So, a
+function called with `(a=1, b=2)` and called with `(b=2, a=1)` will take up two
+entries in the LRU cache even though they are virtually the same function
+invocation.
+
+MicroPython, however, seems to pre-sort keyword arguments.  This means the
+keyword arguments order is lost, and therefore the behaviour of
+`@functools.lru_cache` differs slightly between the two implementations.

python-stdlib/functools/functools.py

@@ -26,3 +26,35 @@ def reduce(function, iterable, initializer=None):
     for element in it:
         value = function(value, element)
     return value
+
+
+def lru_cache(*args, maxsize=128, **kwargs):
+    def o(f):
+        if maxsize == 0:
+            return f
+        values = {}
+        order = []
+
+        def i(*inner_args, **inner_kwargs):
+            # dict isn't hashable and kwargs are pre-sorted by key.
+            key = (inner_args, tuple(inner_kwargs.items()))
+            if key in values:
+                output = values[key]
+                if maxsize:
+                    order.remove(key)
+            else:
+                output = f(*inner_args, **inner_kwargs)
+                if maxsize and len(order) == maxsize:
+                    del values[order.pop()]
+                values[key] = output
+            if maxsize:
+                order.insert(0, key)
+            return output
+
+        return i
+
+    return o(args[0]) if args else o
+
+
+def cache(*args):
+    return lru_cache(*args, maxsize=None)

python-stdlib/functools/manifest.py

@@ -1,3 +1,3 @@
-metadata(version="0.0.7")
+metadata(version="0.1.0")
 
 module("functools.py")

python-stdlib/functools/test_cache.py

@@ -0,0 +1,166 @@
+from functools import lru_cache, cache
+
+
+@lru_cache(maxsize=8)
+def f8(i):
+    global count
+    count += 1
+    return i
+
+
+count = 0
+for i in range(8):
+    assert f8(i) == i
+assert count == 8
+for i in range(8):
+    assert f8(i) == i
+assert count == 8
+
+assert f8(100) == 100
+assert count == 9
+assert f8(5) == 5
+assert count == 9
+assert f8(0) == 0
+assert count == 10
+
+
+@lru_cache
+def fdefault(i):
+    global count
+    count += 1
+    return i
+
+
+count = 0
+for i in range(150):
+    assert fdefault(i) == i
+assert count == 150
+for i in range(149, -1, -1):
+    assert fdefault(i) == i
+assert count == 150 + (150 - 128)
+
+
+@lru_cache(maxsize=0)
+def f0(i):
+    global count
+    count += 1
+    return i
+
+
+count = 0
+for i in range(150):
+    assert f0(i) == i
+assert count == 150
+for i in range(150):
+    assert f0(i) == i
+assert count == 300
+
+
+@lru_cache(maxsize=None)
+def fnone(i):
+    global count
+    count += 1
+    return i
+
+
+count = 0
+for i in range(150):
+    assert fnone(i) == i
+assert count == 150
+for i in range(150):
+    assert fnone(i) == i
+assert count == 150
+
+
+@lru_cache
+def fretnone(i):
+    global count
+    count += 1
+
+
+count = 0
+for i in range(150):
+    assert fretnone(i) is None
+assert count == 150
+for i in range(149, -1, -1):
+    assert fretnone(i) is None
+assert count == 150 + (150 - 128)
+
+
+@lru_cache
+def fargs(i, i2):
+    global count
+    count += 1
+    return i
+
+
+count = 0
+for i in range(150):
+    assert fargs(i, i) == i
+assert count == 150
+for i in range(149, -1, -1):
+    assert fargs(i, i) == i
+assert count == 150 + (150 - 128)
+for i in range(150):
+    assert fargs(i, 10000) == i
+assert count == 150 + (150 - 128) + 150
+
+
+@lru_cache
+def fvarargs(i, *args):
+    global count
+    count += 1
+    return i
+
+
+count = 0
+for i in range(150):
+    if i & 1 == 0:
+        assert fvarargs(i) == i
+    else:
+        assert fvarargs(i, 'micropython') == i
+assert count == 150
+for i in range(149, -1, -1):
+    if i & 1 == 0:
+        assert fvarargs(i) == i
+    else:
+        assert fvarargs(i, 'micropython') == i
+assert count == 150 + (150 - 128)
+for i in range(150):
+    assert fvarargs(i, 'micropython', 'more micropython') == i
+assert count == 150 + (150 - 128) + 150
+
+
+@lru_cache
+def fkwargs(i, i2=None, i3=0, i4="a"):
+    global count
+    count += 1
+    return i
+
+
+count = 0
+for i in range(150):
+    assert fkwargs(i, i3=i) == i
+assert count == 150
+for i in range(149, -1, -1):
+    assert fkwargs(i, i3=i) == i
+assert count == 150 + (150 - 128)
+for i in range(150):
+    assert fkwargs(i, i3=10000) == i
+assert count == 150 + (150 - 128) + 150
+
+
+@cache
+def fcache(i):
+    global count
+    count += 1
+    return i
+
+
+count = 0
+for i in range(150):
+    assert fcache(i) == i
+assert count == 150
+for i in range(150):
+    assert fcache(i) == i
+assert count == 150

tools/ci.sh

@@ -66,6 +66,7 @@ function ci_package_tests_run {
         python-stdlib/collections-defaultdict/test_defaultdict.py \
         python-stdlib/functools/test_partial.py \
         python-stdlib/functools/test_reduce.py \
+        python-stdlib/functools/test_cache.py \
         python-stdlib/heapq/test_heapq.py \
         python-stdlib/hmac/test_hmac.py \
         python-stdlib/itertools/test_itertools.py \