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    Lab 10, Part 3: Inverting a dictionary
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# Lab 10: Inverting a dictionary


## Building a reverse dictionary

<div class='partnerB'>Partner B</div>

Remember the [cs111dict](/labs/lab10/simple-dicts#cs111dict) (click to go to part) dictionary we built earlier in today's 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 function
called `makeCS111Dict` that creates the name:year cs111 dictionary, just like the dictionary you created
at the start of today's lab. 
Since the given <strong>cs111dict</strong> dictionary has student names as keys and graduation
years as values.  The reverse dictionary of <strong>cs111dict</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 `cs111dict` name:year dictionary. Recall
that it contains 101 students.

```py
>>> 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 **cs111dict** dictionary, we get the **inverted** dictionary.
This block of code is commented out in your `invert.py` file in your `lab08` folder (you can umcomment them once you have written your `invertDict` function).
```py
     print("Invert the 111 dict")
     inverted = invertDict(cs111dict)
     print(inverted.keys())
     print("**2021**\n",inverted['2021'])
     print("**2022**\n",inverted['2022'])
     print("**2023**\n",inverted['2023'])
     print("**2024**\n",inverted['2024'])
```
produces this:

```py
Invert the 111 dict
dict_keys(['2024', '2023', '2021', '2022'])
**2021**
 ['Lena', 'Andrea', 'Amal', 'Ronghao', 'Alexandra', 'Rebecca', 
  'Jocelyn', 'Bryant', 'Claire']
**2022**
 ['Rumi', 'Helen', 'Lisa', 'Yujue', 'Maya', 'Ting']
**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']
**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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