Allow memoization to disk for shared processing

#20

.gitignore

@@ -1,2 +1,3 @@
 *.egg-info
 *.pyc
+cached_func_calls/*

proselint/checks/example_check.py

@@ -14,10 +14,13 @@
 The first line always is always wrong.
 
 """
+from proselint.reverse import reverse
 
 
 def check(text):
 
+    reversed_text = reverse(text)
+
     error_code = "PL000"
     msg = "First line always has an error."
 

proselint/memoize.py

@@ -0,0 +1,53 @@
+import os
+import shelve
+import inspect
+import functools
+
+cache_dirname = 'cached_func_calls'
+
+
+def memoize(f):
+    if not os.path.isdir(cache_dirname):
+        os.mkdir(cache_dirname)
+        print 'Created cache directory %s' \
+            % os.path.join(os.path.abspath(__file__), cache_dirname)
+
+    cache_filename = f.__module__ + f.__name__
+    cachepath = os.path.join(cache_dirname, cache_filename)
+
+    try:
+        cache = shelve.open(cachepath, protocol=2)
+    except:
+        print 'Could not open cache file %s, maybe name collision' % cachepath
+        cache = None
+
+    @functools.wraps(f)
+    def wrapped(*args, **kwargs):
+        argdict = {}
+
+        # handle instance methods
+        if hasattr(f, '__self__'):
+            args = args[1:]
+            # argdict['classname'] = f.__self__.__class__
+
+        tempargdict = inspect.getcallargs(f, *args, **kwargs)
+
+        # handle numpy arrays
+        for k, v in tempargdict.iteritems():
+            argdict[k] = v
+
+        key = str(hash(frozenset(argdict.items())))
+
+        try:
+            return cache[key]
+        except KeyError:
+            value = f(*args, **kwargs)
+            cache[key] = value
+            cache.sync()
+            return value
+        except TypeError:
+            print 'Warning: could not disk cache call to %s; it probably has unhashable args' \
+                % (f.__module__ + '.' + f.__name__)
+            return f(*args, **kwargs)
+
+    return wrapped

proselint/reverse.py

@@ -0,0 +1,6 @@
+from memoize import memoize
+
+
+@memoize
+def reverse(text):
+    return text[::-1]