counting

I have a list of Booleans: [True, True, False, False, False, True] and I am looking for a way to count the number of True in the list (so in the example above, I want the return to be 3 .) I have found examples of looking for the number of occurrences of specific elements, but is there a more efficient way to do it since I'm working with Booleans? I'm thinking of something analogous to all or any . True is equal to 1 . >>> sum([True, True, False, False, False, True]) 3 Mark Tolonen list has a count method: >>> [True,True,False].count(True) 2 This is actually more efficient than sum , as well

I currently have the following array: Array( [0] => Array ( [user] => Name 1 [group] => 1 ) [1] => Array ( [user] => Name 2 [group] => 1 ) [2] => Array ( [user] => Name 3 [group] => 2 ) [3] => Array ( [user] => Name 4 [group] => 2 ) [4] => Array ( [user] => Name 5 [group] => 3 ) ) I am attempting to create a new array with the various group values as the key, then count how many are in each group to give the following: Array ( [1] => 2 [2] => 2 [3] => 1 ) I have attempted to use the following, however I get undefined index warnings: $newArr = array(); foreach ($details['user_groups'] as $key =

In Python, I have a list: L = [1, 2, 45, 55, 5, 4, 4, 4, 4, 4, 4, 5456, 56, 6, 7, 67] I want to identify the item that occurred the highest number of times. I am able to solve it but I need the fastest way to do so. I know there is a nice Pythonic answer to this. Andrew Clark Here is a defaultdict solution that will work with Python versions 2.5 and above: from collections import defaultdict L = [1,2,45,55,5,4,4,4,4,4,4,5456,56,6,7,67] d = defaultdict(int) for i in L: d[i] += 1 result = max(d.iteritems(), key=lambda x: x[1]) print result # (4, 6) # The number 4 occurs 6 times Note if L = [1, 2

There are many ways to write a Python program that computes a histogram. By histogram, I mean a function that counts the occurrence of objects in an iterable and outputs the counts in a dictionary. For example: >>> L = 'abracadabra' >>> histogram(L) {'a': 5, 'b': 2, 'c': 1, 'd': 1, 'r': 2} One way to write this function is: def histogram(L): d = {} for x in L: if x in d: d[x] += 1 else: d[x] = 1 return d Are there more concise ways of writing this function? If we had dictionary comprehensions in Python, we could write: >>> { x: L.count(x) for x in set(L) } but since Python 2.6 doesn't have