completed the lab and commited the changed index.ipynb file
Ok, so now that we have a sense of how to read from a list and alter a list in Python, let's put this knowledge to use.
- Practice reading one and multiple elements from lists
- Practice altering data in lists
- Practice adding elements and removing elements from lists
In the previous lesson, we had a list of top travel cities.
top_travel_cities = ['Solta', 'Greenville', 'Buenos Aires', 'Los Cabos', 'Walla Walla Valley', 'Marakesh', 'Albuquerque', 'Archipelago Sea', 'Iguazu Falls', 'Salina Island', 'Toronto', 'Pyeongchang']
Remember to press shift+enter to run each gray block of code (including the one above). Otherwise, the variables will not be defined.
In this lesson we will work with a list of associated countries corresponding to each of the top travel cities.
countries = ['Croatia',
'USA',
'Argentina',
'Mexico',
'USA',
'Morocco',
'New Mexico',
'Finland',
'Argentina',
'Italy',
'Canada',
'South Korea']
Run the code in the cell above by pressing shift + enter.
Ok, so the list of countries associated with each city has been assigned to the variable countries
. Now we will work with reading and manipulating this list.
First, set the variable italy
to be equal to the third to last element from countries
.
Note: If you see an error stating that
countries
is undefined, it means you must press shift+enter in the second gray box wherecountries
variable is assigned.
italy = None # 'Italy'
italy
We assign the varible
italy
equal toNone
, but you should change the wordNone
to code that uses thecountries
list to assignitaly
to'Italy'
. We wrote the variableitaly
a second time, so that you can see what it equals when you run the code block. Currently, nothing is displayed below as it equalsNone
, but when it's correct it will match the string which is commented out,'Italy'
.
italy # 'Italy'
Now access the fourth element and set it equal to the variable mexico
.
mexico = None
mexico
Notice that the second through fifth elements are all in a row and all in the Western Hemisphere. Assign that subset of elements to a variable called kindof_neighbors
.
kindof_neighbors = None
kindof_neighbors
Ok, now let's add a couple of countries onto this list. At the end of the list, add the country 'Malta'.
None # add code here
Then add the country 'Thailand'.
None # add code here
Now your list of countries should look like the following.
countries
# ['Croatia', 'USA', 'Argentina', 'Mexico', 'USA', 'Morocco', 'New Mexico', 'Finland',
# 'Argentina', 'Italy', 'Canada', 'South Korea', 'Malta', 'Thailand']
You may have noticed that "New Mexico" is included in our list of countries. That doesn't seem right. Let's change 'New Mexico' to 'USA'.
None # add code here
countries
# ['Croatia', 'USA', 'Argentina', 'Mexico', 'USA', 'Morocco', 'USA', 'Finland',
# 'Argentina', 'Italy', 'Canada', 'South Korea', 'Malta', 'Thailand']
Finally, let's remove Thailand from the list. No good reason, we're acting on whimsy.
countries = ['Croatia',
'USA',
'Argentina',
'Mexico',
'USA',
'Morocco',
'USA',
'Finland',
'Argentina',
'Italy',
'Canada',
'South Korea',
'Malta',
'Thailand']
countries.pop() # 'Thailand'
countries
# ['Croatia', 'USA', 'Argentina', 'Mexico', 'USA', 'Morocco', 'USA', 'Finland', 'Argentina', 'Italy', 'Canada', 'South Korea', 'Malta']
['Croatia',
'USA',
'Argentina',
'Mexico',
'USA',
'Morocco',
'USA',
'Finland',
'Argentina',
'Italy',
'Canada',
'South Korea',
'Malta']
Ok, now we notice that some countries are mentioned more than once. Let's see how many repeat countries are on this list.
First, use the set
and list
functions to return a unique list of countries. Set this list equal to the variable unique_countries
.
unique_countries = None
unique_countries # ['Canada', 'Italy', 'USA', 'Mexico', 'Finland',
#'Malta', 'Morocco', 'Croatia', 'Argentina', 'South Korea']
Now the number of repeat countries should be the number of countries minus the number of unique countries. So use the len
function on both unique_countries
and countries
to calculate this and assign the result to the variable num_of_repeats
.
num_of_repeats = None
num_of_repeats # 3
In this lesson, we had some practice with working with lists in Python. We saw how to add and remove elements from a list, as well as select specific elements. Finally, we saw how to use a different data structure to calculate the number of unique elements in the list.