You signed in with another tab or window. Reload to refresh your session.You signed out in another tab or window. Reload to refresh your session.You switched accounts on another tab or window. Reload to refresh your session.Dismiss alert
A list is a compound data type; you can group values together, like this:
a = "is" b = "nice" my_list = ["my", "list", a, b]
After measuring the height of your family, you decide to collect some information on the house you're living in. The areas of the different parts of your house are stored in separate variables in the exercise.
@instructions
Create a list, areas, that contains the area of the hallway (hall), kitchen (kit), living room (liv), bedroom (bed) and bathroom (bath), in this order. Use the predefined variables.
Print areas with the print() function.
@hint
You can use the variables that have already been created to build the list: areas = [hall, kit, ...].
Make sure to use square brackets [] rather than parentheses ().
You don't need to use quotation marks when storing variables within a list.
Type print(areas) to print out the list when submitting.
@pre_exercise_code
@sample_code
hall = 11.25 kit = 18.0 liv = 20.0 bed = 10.75 bath = 9.50
# Create list areas
# Print areas
@solution
hall = 11.25 kit = 18.0 liv = 20.0 bed = 10.75 bath = 9.50
# Create list areas areas = [hall, kit, liv, bed, bath]
# Print areas print(areas)
@sct
predef_msg = "Don't remove or edit the predefined variables!" areas_msg = "Define `areas` as the list containing all the area variables, in the correct order: `[hall, kit, liv, bed, bath]`. Watch out for typos. The list shouldn't contain anything else!"
Ex().check_correct( has_printout(0, not_printed_msg = "__JINJA__:Have you used `{{sol_call}}` to print out the `areas` list at the end of your script?"), check_correct( check_object("areas").has_equal_value(incorrect_msg = areas_msg), multi( check_object('hall', missing_msg=predef_msg).has_equal_value(incorrect_msg=predef_msg), check_object('kit', missing_msg=predef_msg).has_equal_value(incorrect_msg=predef_msg), check_object('liv', missing_msg=predef_msg).has_equal_value(incorrect_msg=predef_msg), check_object('bed', missing_msg=predef_msg).has_equal_value(incorrect_msg=predef_msg), check_object('bath', missing_msg=predef_msg).has_equal_value(incorrect_msg=predef_msg) ) ) )
success_msg("Nice! A list is way better here, isn't it?")
Although it's not really common, a list can also contain a mix of Python types including strings, floats, and booleans.
You're now going to add the room names to your list, so you can easily see both the room name and size together.
Some of the code has been provided for you to get you started. Pay attention here! "bathroom" is a string, while bath is a variable that represents the float 9.50 you specified earlier.
@instructions
Finish the code that creates the areas list. Build the list so that the list first contains the name of each room as a string and then its area. In other words, add the strings "hallway", "kitchen" and "bedroom" at the appropriate locations.
Print areas again; is the printout more informative this time?
@hint
The first four elements of the list areas are coded as ["hallway", hall, "kitchen", kit, ....
A string will need to be in quotation marks "".
@pre_exercise_code
@sample_code
hall = 11.25 kit = 18.0 liv = 20.0 bed = 10.75 bath = 9.50
# Adapt list areas areas = [____, hall, ____, kit, "living room", liv, ____, bed, "bathroom", bath]
# Print areas ____
@solution
hall = 11.25 kit = 18.0 liv = 20.0 bed = 10.75 bath = 9.50
# Adapt list areas areas = ["hallway", hall, "kitchen", kit, "living room", liv, "bedroom", bed, "bathroom", bath]
# Print areas print(areas)
@sct
objs = ["hall", "kit", "liv", "bed", "bath"] predef_msg = "Don't remove or edit the predefined variables!" areas_msg = "You didn't assign the correct value to `areas`. Have another look at the instructions. Make sure to place the room name before the variable containing the area each time. The order matters here! Watch out for typos."
Ex().check_correct( check_object("areas").has_equal_value(incorrect_msg = areas_msg), multi([ check_object(obj, missing_msg = predef_msg).has_equal_value(incorrect_msg = predef_msg) for obj in objs]) )
Ex().has_printout(0, not_printed_msg = "__JINJA__:Have you used `{{sol_call}}` to print out the `areas` list at the end of your script?")
success_msg("Nice! This list contains both strings and floats, but that's not a problem for Python!")
As a data scientist, you'll often be dealing with a lot of data, and it will make sense to group some of this data.
Instead of creating a list containing strings and floats, representing the names and areas of the rooms in your house, you can create a list of lists.
Remember: "hallway" is a string, while hall is a variable that represents the float 11.25 you specified earlier.
@instructions
Finish the list of lists so that it also contains the bedroom and bathroom data. Make sure you enter these in order!
Print out house; does this way of structuring your data make more sense?
@hint
Add sublists to the house list by adding ["bedroom", bed] and ["bathroom", bath] inside the square brackets.
Remember to include a comma , after each sublist.
To print a variable x, write print(x) on a new line.
@pre_exercise_code
@sample_code
hall = 11.25 kit = 18.0 liv = 20.0 bed = 10.75 bath = 9.50
# House information as list of lists house = [["hallway", hall], ["kitchen", kit], ["living room", liv], ____, ____]
# Print out house ____
@solution
hall = 11.25 kit = 18.0 liv = 20.0 bed = 10.75 bath = 9.50
# House information as list of lists house = [["hallway", hall], ["kitchen", kit], ["living room", liv], ["bedroom", bed], ["bathroom", bath]]
# Print out house print(house)
@sct
predef_msg = "Don't remove or edit the predefined variables!" house_msg = "You didn't assign the correct value to `house`. Have another look at the instructions. Extend the list of lists so it incorporates a list for each pair of room name and room area. Mind the order and typos!"
Subsetting Python lists is a piece of cake. Take the code sample below, which creates a list x and then selects "b" from it. Remember that this is the second element, so it has index 1. You can also use negative indexing.
x = ["a", "b", "c", "d"] x[1] x[-3] # same result!
Remember the areas list from before, containing both strings and floats? Its definition is already in the script. Can you add the correct code to do some Python subsetting?
@instructions
Print out the second element from the areas list (it has the value 11.25).
Subset and print out the last element of areas, being 9.50. Using a negative index makes sense here!
Select the number representing the area of the living room (20.0) and print it out.
@hint
Use x[1] to select the second element of a list x.
Use x[-1] to select the last element of a list x.
Make sure to wrap your subsetting operations in a print() call.
The number representing the area of the living room is the 6th element in the list, so you'll need [5] here. area[4] would show the string!
@pre_exercise_code
@sample_code
# Create the areas list areas = ["hallway", 11.25, "kitchen", 18.0, "living room", 20.0, "bedroom", 10.75, "bathroom", 9.50]
# Print out second element from areas print(areas[____])
# Print out last element from areas print(areas[____])
# Print out the area of the living room print(areas[____])
@solution
# Create the areas list areas = ["hallway", 11.25, "kitchen", 18.0, "living room", 20.0, "bedroom", 10.75, "bathroom", 9.50]
# Print out second element from areas print(areas[1])
# Print out last element from areas print(areas[-1])
# Print out the area of the living room print(areas[5])
@sct
msg = "Don't remove or edit the predefined `areas` list." Ex().check_object("areas", missing_msg = msg).has_equal_value(incorrect_msg = msg) Ex().has_printout(0, not_printed_msg = "Have another look at your code to print out the second element in `areas`, which is at index `1`.") Ex().has_printout(1, not_printed_msg = "Have another look at your code to print out the last element in `areas`, which is at index `-1`.") Ex().has_printout(2, not_printed_msg = "Have another look at your code to print out the area of the living room. It's at index `5`.") success_msg("Good job!")
Selecting single values from a list is just one part of the story. It's also possible to slice your list, which means selecting multiple elements from your list. Use the following syntax:
my_list[start:end]
The start index will be included, while the end index is not. However, it's also possible not to specify these indexes. If you don't specify the start index, Python figures out that you want to start your slice at the beginning of your list.
@instructions
Use slicing to create a list, downstairs, that contains the first 6 elements of areas.
Create upstairs, as the last 4 elements of areas. This time, simplify the slicing by omitting the end index.
Print both downstairs and upstairs using print().
@hint
Use the brackets [0:6] to get the first six elements of a list.
To get everything except the first 5 elements of a list, l, you would use l[5:].
Add two print() calls to print out downstairs and upstairs.
@pre_exercise_code
@sample_code
# Create the areas list areas = ["hallway", 11.25, "kitchen", 18.0, "living room", 20.0, "bedroom", 10.75, "bathroom", 9.50]
# Use slicing to create downstairs downstairs = areas[____]
# Use slicing to create upstairs upstairs = areas[____]
# Print out downstairs and upstairs ____ ____
@solution
# Create the areas list areas = ["hallway", 11.25, "kitchen", 18.0, "living room", 20.0, "bedroom", 10.75, "bathroom", 9.50]
# Use slicing to create downstairs downstairs = areas[0:6]
# Use slicing to create upstairs upstairs = areas[6:]
# Print out downstairs and upstairs print(downstairs) print(upstairs)
@sct
msg = "Don't remove or edit the predefined `areas` list." Ex().check_object("areas", missing_msg = msg).has_equal_value(incorrect_msg = msg)
patt = "`%s` is incorrect. Use `areas[%s]` and slicing to select the elements you want, or something equivalent." Ex().check_object("downstairs").has_equal_value(incorrect_msg = patt % ('downstairs', '0:6')) Ex().check_object("upstairs").has_equal_value(incorrect_msg = patt % ("upstairs",":6"))
Ex().has_printout(0, not_printed_msg="Have you printed out `downstairs` after calculating it?") Ex().has_printout(1, not_printed_msg="Have you printed out `upstairs` after calculating it?")
success_msg("Great!")
Subsetting lists of lists
type: NormalExercise key: dbbbd306cf xp: 100
A Python list can also contain other lists.
To subset lists of lists, you can use the same technique as before: square brackets. This would look something like this for a list, house:
house[2][0]
@instructions
Subset the house list to get the float 9.5.
@hint
Break this down step by step. First you want to get to the last element of the list, ["bathroom", 9.50]. Recall the index of the last element is -1.
Next you want to get the second element of ["bathroom", 9.50], which is at index 1.
To replace list elements, you subset the list and assign new values to the subset. You can select single elements or you can change entire list slices at once.
For this and the following exercises, you'll continue working on the areas list that contains the names and areas of different rooms in a house.
@instructions
Update the area of the bathroom to be 10.50 square meters instead of 9.50 using negative indexing.
Make the areas list more trendy! Change "living room" to "chill zone". Don't use negative indexing this time.
@hint
To update the bathroom area, identify the subset of the bathroom area (it's the last item of the list!).
Then, replace the value with the new bathroom area by assigning it to this subset.
Do the same to update the "living room" name, which is at index 4.
@pre_exercise_code
@sample_code
# Create the areas list areas = ["hallway", 11.25, "kitchen", 18.0, "living room", 20.0, "bedroom", 10.75, "bathroom", 9.50]
# Correct the bathroom area
# Change "living room" to "chill zone"
@solution
# Create the areas list areas = ["hallway", 11.25, "kitchen", 18.0, "living room", 20.0, "bedroom", 10.75, "bathroom", 9.50]
bathroom_msg = 'You can use `areas[-1] = 10.50` to update the bathroom area.' chillzone_msg = 'You can use `areas[4] = "chill zone"` to update the living room name.' Ex().check_correct( check_object('areas').has_equal_value(incorrect_msg = 'Your changes to `areas` did not result in the correct list. Are you sure you used the correct subset operations? When in doubt, you can use a hint!'), multi( has_equal_value(expr_code='areas[-1]', override=10.50, incorrect_msg = bathroom_msg), has_equal_value(expr_code='areas[4]', override='chill zone', incorrect_msg = chillzone_msg), ) ) success_msg('Sweet! As the code sample showed, you can also slice a list and replace it with another list to update multiple elements in a single command.')
If you can change elements in a list, you sure want to be able to add elements to it, right? You can use the + operator:
x = ["a", "b", "c", "d"] y = x + ["e", "f"]
You just won the lottery, awesome! You decide to build a poolhouse and a garage. Can you add the information to the areas list?
@instructions
Use the + operator to paste the list ["poolhouse", 24.5] to the end of the areas list. Store the resulting list as areas_1.
Further extend areas_1 by adding data on your garage. Add the string "garage" and float 15.45. Name the resulting list areas_2.
@hint
Follow the code sample in the assignment. x is areas here, and ["e", "f"] is ["poolhouse", 24.5].
To add more elements to areas_1, use areas_1 + ["element", 123].
@pre_exercise_code
@sample_code
# Create the areas list and make some changes areas = ["hallway", 11.25, "kitchen", 18.0, "chill zone", 20.0, "bedroom", 10.75, "bathroom", 10.50]
# Add poolhouse data to areas, new list is areas_1 areas_1 = ____
# Add garage data to areas_1, new list is areas_2 areas_2 = ____
@solution
# Create the areas list (updated version) areas = ["hallway", 11.25, "kitchen", 18.0, "chill zone", 20.0, "bedroom", 10.75, "bathroom", 10.50]
# Add poolhouse data to areas, new list is areas_1 areas_1 = areas + ["poolhouse", 24.5]
# Add garage data to areas_1, new list is areas_2 areas_2 = areas_1 + ["garage", 15.45]
@sct
msg = "Don't remove or edit the predefined `areas` list." Ex().check_object("areas", missing_msg = msg).has_equal_value(incorrect_msg = msg) Ex().check_object("areas_1").has_equal_value(incorrect_msg = "Use `areas + [\"poolhouse\", 24.5]` to create `areas_1`. Watch out for typos!") Ex().check_object("areas_2").has_equal_value(incorrect_msg = "Use `areas_1 + [\"garage\", 15.45]` to create `areas_2`. Watch out for typos!") success_msg("Cool! The list is shaping up nicely!")
Delete list elements
type: NormalExercise key: 85f792356e xp: 100
Finally, you can also remove elements from your list. You can do this with the del statement:
x = ["a", "b", "c", "d"] del x[1]
Pay attention here: as soon as you remove an element from a list, the indexes of the elements that come after the deleted element all change!
Unfortunately, the amount you won with the lottery is not that big after all and it looks like the poolhouse isn't going to happen. You'll need to remove it from the list. You decide to remove the corresponding string and float from the areas list.
@instructions
Delete the string and float for the "poolhouse" from your areas list.
Print the updated areas list.
@hint
You'll need to use del twice to delete two elements. Be careful about changing indexes though!
Ex().has_printout(0, not_printed_msg="Have you printed out `areas` after removing the poolhouse string and float?") success_msg("Correct! You'll learn about easier ways to remove specific elements from Python lists later on.")
Some code has been provided for you in this exercise: a list with the name areas and a copy named areas_copy.
Currently, the first element in the areas_copy list is changed and the areas list is printed out. If you hit the run code button you'll see that, although you've changed areas_copy, the change also takes effect in the areas list. That's because areas and areas_copy point to the same list.
If you want to prevent changes in areas_copy from also taking effect in areas, you'll have to do a more explicit copy of the areas list with list() or by using [:].
@instructions
Change the second command, that creates the variable areas_copy, such that areas_copy is an explicit copy of areas. After your edit, changes made to areas_copy shouldn't affect areas. Submit the answer to check this.
@hint
Change the areas_copy = areas call. Instead of assigning areas, you can assign list(areas) or areas[:].
@pre_exercise_code
@sample_code
# Create list areas areas = [11.25, 18.0, 20.0, 10.75, 9.50]
# Change this command areas_copy = areas
# Change areas_copy areas_copy[0] = 5.0
# Print areas print(areas)
@solution
# Create list areas areas = [11.25, 18.0, 20.0, 10.75, 9.50]
# Change this command areas_copy = list(areas)
# Change areas_copy areas_copy[0] = 5.0
# Print areas print(areas)
@sct
Ex().check_correct( check_object("areas_copy").has_equal_value(incorrect_msg = "It seems that `areas_copy` has not been updated correctly."), check_function("list", missing_msg = "Make sure to use `list(areas)` to create an `areas_copy`.") )
mmsg = "Don't remove the predefined `areas` list." imsg = "Be sure to edit ONLY the copy, not the original `areas` list. Have another look at the exercise description if you're unsure how to create a copy." Ex().check_correct( check_object("areas", missing_msg = mmsg).has_equal_value(incorrect_msg = imsg), check_function("list", missing_msg = "Make sure to use `list(areas)` to create an `areas_copy`.") )
success_msg("Nice! The difference between explicit and reference-based copies is subtle, but can be really important. Try to keep in mind how a list is stored in the computer's memory.")