from sys import version_info as pyver
class Tally:
"""
A tally or histogram class
Counts the occurances of objects (hashables only) given to it.
The number of seen samples is stored in the object's samples
instance variable.
"""
def __init__(self):
self.samples = 0L
self.values = {}
def incr(self, k, amount = 1):
"""
Increase count for k
"""
self.samples += 1
self.values[k] = self.values.get(k, 0) + amount
def decr(self, k, amount = 1):
"""
Decrease count for k
"""
self.samples += 1
self.values[k] = self.values.get(k, 0) - amount
def val(self, k):
"""
Return count for k
"""
return self.values.get(k, 0)
def getkeys(self):
"""
Return all histogram keys
"""
return self.values.keys()
def counts(self, desc = False):
'''
Return list of keys, sorted by values.
If desc is True, return a descending sort.
'''
if (pyver[0] < 2) or (pyver[0] == 2 and pyver[1] < 4):
# This is for Python versions <2.4
i = map(lambda items: list(items), self.values.items())
map(lambda rev: rev.reverse(), i)
i.sort()
if desc:
i.reverse()
return i
else:
# This only works with Python >=2.4 but is much
# faster than the code above.
return sorted(( list(reversed(items)) \
for items in self.values.iteritems() ), reverse = desc)
