4 .. At the end of this tutorial, you will be able to |
4 .. At the end of this tutorial, you will be able to |
5 |
5 |
6 .. 1. Create dictionaries |
6 .. 1. Create dictionaries |
7 .. #. Add data to dictionaries |
7 .. #. Add data to dictionaries |
8 .. #. Retrieve data |
8 .. #. Retrieve data |
9 .. #. Familiarize using ``.keys()`` and ``.values()`` methods |
9 .. #. use ``.keys()`` and ``.values()`` methods |
10 .. #. Checking for container-ship of keys |
10 .. #. Check for container-ship of keys |
11 .. #. Iterating over elements |
11 .. #. Iterate over elements |
12 |
12 |
13 .. Prerequisites |
13 .. Prerequisites |
14 .. ------------- |
14 .. ------------- |
15 |
15 |
16 .. 1. should have ``ipython`` installed. |
16 .. 1. should have ``ipython`` installed. |
47 indexes, dictionaries have keys or strings as indexes. |
48 indexes, dictionaries have keys or strings as indexes. |
48 |
49 |
49 Before we can proceed, start your IPython interpreter with the |
50 Before we can proceed, start your IPython interpreter with the |
50 ``-pylab`` option. |
51 ``-pylab`` option. |
51 |
52 |
|
53 .. #[Puneeth: We don't need pylab] |
|
54 |
52 {{{ start ipython interpreter by issuing command ipython -pylab }}} |
55 {{{ start ipython interpreter by issuing command ipython -pylab }}} |
53 |
56 |
54 {{{ switch to next slide, Creating dictionary }}} |
57 {{{ switch to next slide, Creating dictionary }}} |
55 |
58 |
56 Let us start by creating an empty dictionary, type the following in |
59 Let us start by creating an empty dictionary, type the following in |
57 your IPython interpreter. |
60 your IPython interpreter. |
58 :: |
61 :: |
59 |
62 |
60 mt_dict = {} |
63 mt_dict = {} |
61 |
64 |
62 Notice that unlike lists curly braces are used define ``dictionary``, |
65 Notice that unlike lists, curly braces are used define ``dictionary``. |
63 |
66 |
64 {{{ move the mouse over curly braces to grab attention }}} |
67 {{{ move the mouse over curly braces to grab attention }}} |
65 |
68 |
66 Now let us see how to create a filled dictionary, |
69 Now let us see how to create a non-empty dictionary, |
67 :: |
70 :: |
68 |
71 |
69 extensions = {'jpg' : 'JPEG Image', 'py' : 'Python script', 'html' : 'Html document', 'pdf' : 'Portable Document Format'} |
72 extensions = {'jpg' : 'JPEG Image', 'py' : 'Python script', 'html' : 'Html document', 'pdf' : 'Portable Document Format'} |
70 |
73 |
71 Notice that each key-value pair is separated by a comma |
74 Notice that each key-value pair is separated by a comma |
144 :: |
147 :: |
145 |
148 |
146 'py' in extensions |
149 'py' in extensions |
147 'odt' in extensions |
150 'odt' in extensions |
148 |
151 |
149 So in short it will return ``True`` if the key is found in the |
152 It will return ``True`` if the key is found in the dictionary, and |
150 dictionary, and will return ``False`` if key is not present. Note that |
153 will return ``False`` if key is not present. Note that we can check |
151 we can check only for container-ship of keys in dictionaries and not |
154 only for container-ship of keys in dictionaries and not values. |
152 values. |
|
153 |
155 |
154 {{{ switch to next slide, Retrieve keys and values }}} |
156 {{{ switch to next slide, Retrieve keys and values }}} |
155 |
157 |
156 Now let us see how to retrieve the keys and values. We can use the |
158 Now let us see how to retrieve the keys and values. We can use the |
157 method ``keys()`` for getting a list of the keys in a particular |
159 method ``keys()`` for getting a list of the keys in a particular |