Using Python Dictionaries

Our first few tasks require us to create the emails variable that we're going to work with throughout the lab and then add some information to it. Here's how we complete the first task:

using-dictionaries.py (partial)

# 1) Set the emails variable to be an empty dictionary
emails = {}

assert emails == {}, f"Expected `emails` to be {{}} but got: {repr(users)}"

Now if we run the file (python3.7 using-dictionaries.py), we should see the error for the second task:

$ python3.7 using-dictionaries.py
Traceback (most recent call last):
  File "using-dictionaries.py", line 12, in <module>
    }, f"Expected `emails` to be {{'ashley': '[email protected]', 'craig': '[email protected]', 'elizabeth': '[email protected]'}} but got: {repr(emails)}"
AssertionError: Expected `emails` to be {'ashley': '[email protected]', 'craig': '[email protected]', 'elizabeth': '[email protected]'} but got: {}

This error shows us that we need to add values to the dictionary before we can continue. The task also specifies that we shouldn't just reassign the emails variable. Here's an example solution to this:

using-dictionaries.py (partial)

# 2) Add 'ashley', 'craig', and 'elizabeth' to the emails dictionary without reassigning the variable.

emails['ashley'] = '[email protected]'
emails['craig'] = '[email protected]'
emails['elizabeth'] = '[email protected]'

assert emails == {
    'ashley': '[email protected]',
    'craig': '[email protected]',
    'elizabeth': '[email protected]'
}, f"Expected `emails` to be {{'ashley': '[email protected]', 'craig': '[email protected]', 'elizabeth': '[email protected]'}} but got: {repr(emails)}"

For tasks 3 and 4, we need to remove the craig key/value pair and add one called dalton. Here's an example solution for getting rid of craig:

using-dictionaries.py (partial)

# 3) Remove 'craig' from the emails dictionary without reassigning the variable.
del emails["craig"]

assert emails == {
    "ashley": "[email protected]",
    "elizabeth": "[email protected]",
}, f"Expected `emails` to be {{'ashley': '[email protected]', 'elizabeth': '[email protected]'}} but got: {repr(emails)}"

When we run the script again, we'll get an error about it expecting a dalton. To fix that, we need to add it in. Here's how:

# 4) Add 'dalton' to the emails dictionary without reassigning the variable.

emails["dalton"] = "[email protected]"

assert emails == {
    "ashley": "[email protected]",
    "elizabeth": "[email protected]",
    "dalton": "[email protected]",
}, f"Expected `emails` to be {{'ashley': '[email protected]', 'elizabeth': '[email protected]', 'dalton': '[email protected]'}} but got: {repr(emails)}"

The del statement will allow us to remove an item with the specified key to complete task three. For task four, we've just added add another key/value pair.

For tasks five and six we'll be extracting information from the emails dictionary to populate new lists for users and email_list. The users list will contain all of the keys from emails and the email_list will include all of the values.

using-dictionaries.py (partial)

# 5) Return a list of keys from the emails dictionary as `users`
users = list(emails.keys())

assert users == [
    "ashley",
    "elizabeth",
    "dalton",
], f"Expected `users` to be ['ashley', 'elizabeth', 'dalton'] but got: {repr(users)}"

# 6) Return a list of values from the emails dictionary as `email_list`
email_list = list(emails.values())

assert email_list == [
    "[email protected]",
    "[email protected]",
    "[email protected]",
], f"Expected `email_list` to be ['[email protected]', '[email protected]', '[email protected]'] but got: {repr(email_list)}"

For the final task, we'll extract a new list called pairs from emails that will include a 2-tuple for each key/value pair in the emails dictionary.

using-dictionaries.py (partial)

# 7) Return a list of tuples called `pairs` representing the key/value pairs in `emails`.
pairs = list(emails.items())

assert pairs == [
    ("ashley", "[email protected]"),
    ("elizabeth", "[email protected]"),
    ("dalton", "[email protected]"),
], f"Expected `pairs` to be [('ashley', '[email protected]'), ('elizabeth', '[email protected]'), ('dalton', '[email protected]')] but got: {repr(pairs)}"