In [3]:
# Let's parse the data from the last mission as an example.
# First, we open the wait times file from the last mission.
f = open("crime_rates.csv", 'r')
data = f.read()
rows = data.split('\n')
full_data = []
for row in rows:
split_row = row.split(",")
full_data.append(split_row)
weather_data = []
f = open("la_weather.csv", 'r')
data = f.read()
rows = data.split('\n')
full_data = []
for row in rows:
split_row = row.split(",")
weather_data.append(split_row)
print(weather_data[:10])
In [4]:
# The "days" column in our data isn't extremely useful for our task, so we need to just grab the second column, with the weather.
# We looped over lists before, and this is how we will extract the second column.
lolist = [[1,2],[3,4],[5,6],[7,8]]
second_column = []
for item in lolist:
# Each item in lolist is a list.
# We can get just the second column value by indexing the item.
value = item[1]
second_column.append(value)
# second_column is now a list containing only values from the second column of lolist.
print(second_column)
# Let's read in our weather data again.
weather_data = []
f = open("la_weather.csv", 'r')
data = f.read()
rows = data.split('\n')
for row in rows:
split_row = row.split(",")
weather_data.append(split_row)
weather_column = []
for row in weather_data:
val = row[1]
weather_column.append(val)
print(weather_column)
In [5]:
weather = weather_column
In [7]:
# In order to make it easier to use the weather column that we just parsed, we're going to automatically include it from now on.
# It's been specially added before our code runs.
# We can interact with it normally -- it's a list.
print(weather[0])
count = len(weather)
print(count)
In [9]:
# Let's practice with some list slicing.
a = [4,5,6,7,8]
# New list containing index 2 and 3.
print(a[2:4])
# New list with no elements.
print(a[2:2])
# New list containing only index 2.
print(a[2:3])
slice_me = [7,6,4,5,6]
slice1 = slice_me[2:4]
slice2 = slice_me[1:2]
slice3 = slice_me[3:]
print(slice1, slice2, slice3)
In [10]:
new_weather = weather[1:]
print(new_weather)
In [12]:
# We can make a dictionary with curly braces.
dictionary_one = {}
# The we can add keys and values.
dictionary_one["key_one"] = 2
print(dictionary_one)
# Keys and values can be anything.
# And dictionaries can have multiple keys
dictionary_one[10] = 5
dictionary_one[5.2] = "hello"
print(dictionary_one)
dictionary_two = {
"test": 5,
10: "hello"
}
print(dictionary_two)
In [15]:
dictionary_one = {}
dictionary_one["test"] = 10
dictionary_one["key"] = "fly"
# We can retrieve values from dictionaries with square brackets.
print(dictionary_one["test"])
print(dictionary_one["key"])
dictionary_two = {}
dictionary_two["key1"] = "high"
dictionary_two["key2"] = 10
dictionary_two["key3"] = 5.6
a, b, c = dictionary_two["key1"], dictionary_two["key2"], dictionary_two["key3"]
print(a, b, c)
Make a dictionary c with the keys 7, 8, and 9 corresponding to the values "raven", "goose", and "duck". Make a dictionary d with the keys "morning", "afternoon", "evening", and "night" corresponding to the values 9, 14, 19, and 23 respectively.
In [16]:
# We can define dictionaries that already contain values.
# All we do is add in keys and values separated by colons.
# We have to separate pairs of keys and values with commas.
a = {"key1": 10, "key2": "indubitably", "key3": "dataquest", 3: 5.6}
# a is initialized with those keys and values, so we can access them.
print(a["key1"])
# Another example
b = {4: "robin", 5: "bluebird", 6: "sparrow"}
print(b[4])
c = {
7: "raven",
8: "goose",
9: "duck"
}
d = {
"morning": 9,
"afternoon": 14,
"evening": 19,
"night": 23
}
print(c, d)
In [17]:
# We can check if values are in lists using the in statement.
the_list = [10,60,-5,8]
# This is True because 10 is in the_list
print(10 in the_list)
# This is True because -5 is in the_list
print(-5 in the_list)
# This is False because 9 isn't in the_list
print(9 in the_list)
# We can assign the results of an in statement to a variable.
# Just like any other boolean.
a = 7 in the_list
list2 = [8, 5.6, 70, 800]
c, d, e = 9 in list2, 8 in list2, -1 in list2
print(c, d, e)
In [18]:
# We can check if a key is in a dictionary with the in statement.
the_dict = {"robin": "red", "cardinal": "red", "oriole": "orange", "lark": "blue"}
# This is True
print("robin" in the_dict)
# This is False
print("crow" in the_dict)
# We can also assign the boolean to a variable
a = "cardinal" in the_dict
print(a)
dict2 = {"mercury": 1, "venus": 2, "earth": 3, "mars": 4}
b = "jupiter" in dict2
c = "earth" in dict2
print(b, c)
In [19]:
# The code in an else statement will be executed if the if statement boolean is False.
# This will print "Not 7!"
a = 6
# a doesn't equal 7, so this is False.
if a == 7:
print(a)
else:
print("Not 7!")
# This will print "Nintendo is the best!"
video_game = "Mario"
# video_game is "Mario", so this is True
if video_game == "Mario":
print("Nintendo is the best!")
else:
print("Sony is the best!")
season = "Spring"
if season == "Summer":
print("It's hot!")
else:
print("It might be hot!")
In [ ]:
# We can count how many times items appear in a list using dictionaries.
pantry = ["apple", "orange", "grape", "apple", "orange", "apple", "tomato", "potato", "grape"]
# Create an empty dictionary
pantry_counts = {}
# Loop through the whole list
for item in pantry:
# If the list item is already a key in the dictionary, then add 1 to the value of that key.
# This is because we've seen the item again, so our count goes up.
if item in pantry_counts:
pantry_counts[item] = pantry_counts[item] + 1
else:
# If the item isn't already a key in the count dictionary, then add the key, and set the value to 1.
# We set the value to 1 because we are seeing the item, so it's occured once already in the list.
pantry_counts[item] = 1
print(pantry_counts)
us_presidents = ["Adams", "Bush", "Clinton", "Obama", "Harrison", "Taft", "Bush", "Adams", "Wilson", "Roosevelt", "Roosevelt"]
us_president_counts = {}
for p in us_presidents:
if p not in us_president_counts:
us_president_counts[p] = 0
us_president_counts[p] += 1
print(us_president_counts)