Merge lp:~brunogirin/python-snippets/bzhbranch into lp:~jonobacon/python-snippets/trunk

[Bruno Girin]

[Bruno Girin (brunogirin)]

Added a list 101 that includes examples of most operations on lists.

=== added file 'pythoncore/lists101.py'
--- pythoncore/lists101.py	1970-01-01 00:00:00 +0000
+++ pythoncore/lists101.py	2010-02-27 22:07:16 +0000
@@ -0,0 +1,91 @@
+#!/usr/bin/env python
+#
+# [SNIPPET_NAME: Lists 101]
+# [SNIPPET_CATEGORIES: Python Core]
+# [SNIPPET_DESCRIPTION: Basic and not so basic list operations]
+# [SNIPPET_AUTHOR: Bruno Girin <[e-mail]>]
+# [SNIPPET_LICENSE: GPL]
+
+# This snippet demonstrates how the basics on lists: how to create, add,
+# remove items, get items or slices, sort, etc.
+
+#
+# First, let's create simple list
+#
+print "Create a simple list"
+simpleList = ["Karmic", "Lucid", "Hardy", "Jaunty", "Intrepid"]
+# print it
+print simpleList
+#
+# Interrogate the list
+#
+print "\nInterrogate the list"
+# get item 3:  lists start counting at 0 so it should be Jaunty
+print simpleList[3]
+# we can also get a slice
+print simpleList[2:4]
+# get the first three items
+print simpleList[:3]
+# or all items from number index 3 (which is the fourth item) to the end
+print simpleList[3:]
+# we can also take every other item, as a slice is defined
+# like this: start:stop:step
+print simpleList[::2]
+# get the length of the list
+print len(simpleList)
+# we can get the index of an item in the list
+print simpleList.index("Hardy")
+# and when the list doesn't contain the item, we get an error that we can catch
+try:
+    print simpleList.index("Feisty")
+except ValueError:
+    print "The list doesn't contain the item Feisty"
+#
+# Modify the list
+#
+print "\nModify the list"
+# add another item
+simpleList.append("Twisty")
+print simpleList
+# oops! let's sort this out by replacing in place
+simpleList[5] = "Gutsy"
+print simpleList
+# extend the list with another one
+otherList = ["Edgy", "Breezy"]
+simpleList.extend(otherList)
+print simpleList
+# remove an item from the list (Hardy should not be in the list anymore)
+del simpleList[2]
+print simpleList
+# insert an item in the middle of the list
+simpleList.insert(4, "Hardy")
+print simpleList
+# remove an item by its value rather than its index
+simpleList.remove("Edgy")
+print simpleList
+#
+# Create modified copies of the list
+#
+print "\nCreate modified copies of the list"
+# sort it
+print sorted(simpleList)
+# join it to produce a custom print
+print ' => '.join(sorted(simpleList))
+# lists can contain the same item several times so if we add Lucid again:
+simpleList.append("Lucid")
+# we have it twice in the list (easier to see if we sort it)
+print sorted(simpleList)
+# but we can get round that by transforming it into a set, which is a list
+# with no duplicates; and of course we can also sort the set
+print sorted(set(simpleList))
+#
+# Iterate over the list
+#
+print "\nIterate over the list"
+for i in simpleList:
+    print i.upper()
+# but if we want to create another list by applying the same expression to
+# each item, we can use a list comprehension
+upList = [i.upper() for i in sorted(set(simpleList))]
+print upList
+