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    Lab 11, Part 2: Inverting a dictionary
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# Lab 11: Inverting a dictionary

## Building a reverse dictionary
Remember the [cs111dict](/labs/lab08/simple-dicts#cs111dict) (click to go to that lab) dictionary we built during our last lab?
 Wouldn't it be cool to be able to create a reverse
   dictionary where we use the values as the keys? We will return a
   dictionary where the keys are what used to be the values, and each
   key has a list of associated values (original keys).  

Open the file `invert.py`. At the top of the `invert.py` file, there is a block of code to load
in a pre-existing name:year dictionary called `cs111`. Just like the dictionary you created
at the start of today's lab, 
the given <strong>cs111</strong> dictionary has student names as keys and graduation
years as values.  The reverse dictionary of <strong>cs111</strong>
will have the graduation years as keys and the students' names
associated with those graduation years as values.  

For example,

Let's take a look at the original `cs111` name:year dictionary:


```py
>>> len(cs111)
101
>>> cs111dict.values()
dict_values(['2024', '2023', '2024', '2024', '2023', '2024', 
'2023', '2024', '2024', '2023', '2023', '2024', '2024', 
'2023', '2024', '2021', '2024', '2024', '2023', '2023', 
'2024', '2024', '2024', '2023', '2023', '2023', '2022', 
'2024', '2023', '2023', '2024', '2024', '2024', '2024', 
'2024', '2024', '2023', '2024', '2024', '2023', '2023', 
'2021', '2024', '2024', '2021', '2021', '2021', '2024', 
'2024', '2024', '2024', '2024', '2022', '2023', '2024', 
'2023', '2024', '2024', '2024', '2024', '2022', '2024', 
'2023', '2024', '2023', '2023', '2024', '2024', '2021', 
'2022', '2024', '2023', '2024', '2024', '2023', '2024', 
'2023', '2023', '2023', '2024', '2024', '2024', '2024', 
'2021', '2022', '2023', '2023', '2024', '2024', '2024', 
'2023', '2021', '2022', '2024', '2024', '2021', '2023', 
'2024', '2023', '2023', '2024'])

```
Now, if we invert the original **cs111** dict, we get the **inverted** dict.

```py
>>> inverted = invertDict(cs111)
>>> inverted.keys()
dict_keys(['2024', '2023', '2021', '2022'])

>>> inverted['2021']
['Lena', 'Andrea', 'Amal', 'Ronghao', 'Alexandra', 'Rebecca', 'Jocelyn', 'Bryant', 'Claire']

>>> inverted['2022']
['Rumi', 'Helen', 'Lisa', 'Yujue', 'Maya', 'Ting']

>>> inverted['2023']
'Sarah', 'Jiyoung', 'Parul', 'Briana', 'Liliana', 'Dakota', 'Cecilia', 
'Sophie', 'Dina', 'Emilia', 'Erica', 'Ananya', 'Julia', 'Grace', 'Chelsea', 
'Juliette', 'Dominique', 'Molly', 'Chae', 'Marissa', 'Daisy', 'Aisha', 
'Kealani', 'Preeda', 'Sapphire', 'Mira', 'Sadie', 'Havannah', 'Alyssa', 
'Amelia', 'Emma', 'Lily']

>>> inverted['2024']
['Karina', 'Jamie', 'Angela', 'Lauren', 'Elizabeth', 'Edith', 'Calla', 
'Eunji', 'Annabel', 'Maura', 'Charlotte', 'Lea', 'Victoria', 'Meha', 'Keiko', 
'Diana', 'Anah', 'Youngja', 'Shan', 'Joy', 'Makiko', 'Sabina', 'Paige', 
'Kalau', 'Isabella', 'HeeJoo', 'Breana', 'Ana', 'Jingyuan', 'Nicole', 'Hope', 
'Susanna', 'Daneen', 'Isabelle', 'Hongyu', 'Fiona', 'Maggie', 'Amanda', 
'Jennifer', 'Hannah', 'Aine', 'Trisha', 'Rune', 'Yuwei', 'Seana', 'Alice', 
'Sophia', 'Kristi', 'Kathryn', 'Zoe', 'Lola', 'Maddy', 'Aimee', 'Savannah']


```

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