new tasks

Task/Collections/Python/collections.py

@@ -0,0 +1,20 @@
+collection = [0, '1']                 # Lists are mutable (editable) and can be sorted in place
+x = collection[0]                     # accessing an item (which happens to be a numeric 0 (zero)
+collection.append(2)                  # adding something to the end of the list
+collection.insert(0, '-1')            # inserting a value into the beginning
+y = collection[0]                     # now returns a string of "-1"
+collection.extend([2,'3'])            # same as [collection.append(i) for i in [2,'3']] ... but faster
+collection += [2,'3']                 # same as previous line
+collection[2:6]                       # a "slice" (collection of the list elements from the third up to but not including the sixth)
+len(collection)                       # get the length of (number of elements in) the collection
+collection = (0, 1)                   # Tuples are immutable (not editable)
+collection[:]                         # ... slices work on these too; and this is equivalent to collection[0:len(collection)]
+collection[-4:-1]                     # negative slices count from the end of the string
+collection[::2]                       # slices can also specify a stride --- this returns all even elements of the collection
+collection="some string"              # strings are treated as sequences of characters
+x = collection[::-1]                  # slice with negative step returns reversed sequence (string in this case).
+collection[::2] == "some string"[::2] # True, literal objects don't need to be bound to name/variable to access slices or object methods
+collection.__getitem__(slice(0,len(collection),2))  # same as previous expressions.
+collection = {0: "zero", 1: "one"}    # Dictionaries (Hash)
+collection['zero'] = 2                # Dictionary members accessed using same syntax as list/array indexes.
+collection = set([0, '1'])            # sets (Hash)