Basic Python Flashcards
(111 cards)
Write a lambda function that adds a column to the dataframe ‘shoes’ that returns Not Vegan if the shoe is made out of leather and Vegan if it is not.
df[‘vegan’] = df.shoe_type.apply(lambda x: ‘Not_Vegan’ if x == ‘Leather’ else ‘Vegan’)
Use the columns ‘gender’ and ‘last_name’ from ‘df’ to make a new column called ‘salutation’ that returns ‘Dear Mr.’ and the last name if gender is male or ‘Dear Ms.’ and last name if female.
df[‘salutations’] = df.apply(lambda row: “Dear Mr. “ + row.last_name if row.gender == ‘male’ else “Dear Ms. “, axis = 1)
Get the last name only from a column that has the format “Skye Long” called “name”
get_last_name = lambda x: x.split()[-1]
df[‘last_name’] = df.name.apply(get_last_name)
Rename individual, compared to all, columns in a df
df.rename(columns = {‘old’:’new, ‘old2’:’new2’}, inplace = True)
Rename the following columns in order:
name, last name, user
df.columns = [‘first_name’, ‘last_name’, ‘id’]
Only works if you have the same # of columns as in the original. You can also accidentally overwrite something. Better to use the df.rename(columns={old:new}, inplace = True).
What would this produce:
[1,2] + [3,4]
[1,2,3,4]
What is the simple syntax to apply lambda to a row in a dataframe?
df.apply(lambda row: “what will be returned” row[‘name of row to act on’] , axis = 1)
Example:
total_earned = lambda row: (row.hourly_wage * 40) + ((row.hourly_wage * 1.5) * (row.hours_worked - 40)) if row.hours_worked > 40 else row.hourly_wage * row.hours_worked
df[‘total_earned’] = df.apply(total_earned, axis = 1)
Here the lambda is written seperatly, but it could be combined
What is the syntax for the .apply attribute?
df.col.apply(func)
EXample:
get_last_name = lambda x: x.split()[-1]
df[‘last_name’] = df.name.apply(get_last_name)
df.apply(row func, axis = 1)
Nested List Comprehensions
List 1 = [0,1,2,3,4,5]
List2 = [‘a’,’b’,’c’,’d’,’e’,’f’]
I want the value of list 2 for every value of list 1 that is less than 3
new_list = [list2[i] for i in range (0, len(list2)) if list1[i] < 3]
Create a new list named double_nums by multiplying each number in nums by two
nums = [4, 8, 15, 16, 23, 42]
double_nums = [i * 2 for i in nums]
create a list from 0 to 5
new_list = range(6)
Write this for loop as a list comp:
for x in l:
if x>=45: x+1
else: x+5
[x+1 if x >=45 else x + 5 for x in l]
Write this as an if statement
[x+1 for x in l if x >= 45]
if x >= 45:
x+1
What will this code produce?
nums = [4, 8, 15, 16, 23, 42]
parity = [0 if i%2 == 0 else 1 for i in nums]
print(parity)
[0, 0, 1, 0, 1, 0]
Write this as a list comp:
nums2 = [4, 8, 15, 16, 23, 42]
parity2 = []
for i in nums2:
if i%2 == 0:
parity2.append(0)
else:
parity2.append(1)
parity = [0 if i%2 == 0 else 1 for i in nums]
If numbers are above 45 then add 1, if num <10 subtract 1, else add 5
l = [22, 13, 45, 50, 98, 69, 43, 44, 1]
for i in l:
if i >45:
l_2.append(i+1)
elif i
l_2.append(i-1)
else:
l_2.append(i+5)
print(l_2)
l_3 = [i+1 if i > 45 else (i-1 if i<10 else i+5) for i in l]
Create a new list named first_character that contains the first character from every name in the list names
names = [“Elaine”, “George”, “Jerry”, “Cosmo”]
names = [“Elaine”, “George”, “Jerry”, “Cosmo”]
first_character = [i[0] for i in names]
print(first_character)
Create a new list called greater_than_two, in which an entry at position i is True if the entry in nums at position i is greater than 2.
nums = [5, -10, 40, 20, 0]
greater_than_two = [True if i >2 else False for i in nums]
print(greater_than_two)
Create a new list named product that contains the product of each sub-list of nested_lists
product = [x1 * x2 for (x1, x2) in nested_lists]
Create a new list named greater_than that contains True if the first number in the sub-list is greater than the second number in the sub-list, and False otherwise.
nested_lists = [[4, 8], [16, 15], [23, 42]]
greater_than = [True if x1 > x2 else False for (x1, x2) in nested_lists]
Create a new list named first_only that contains the first element in each sub-list of nested_lists.
nested_lists = [[4, 8], [16, 15], [23, 42]]
first_only = [x1 for (x1, x2) in nested_lists]
Use list comprehension and the zip function to create a new list named sums that sums corresponding items in lists a and b. For example, the first item in the new list should be 5 from adding 1 and 4 together.
a = [1.0, 2.0, 3.0]
b = [4.0, 5.0, 6.0]
sums = [x1 + x2 for (x1, x2) in zip(a,b)]
You’ve been given two lists: a list of capitals and a list of countries. Create a new list named locations that contains the string “capital, country” for each item in the original lists. For example, if the 5th item in the capitals list is “Lima” and the 5th item in the countries list is “Peru”, then the 5th item in the new list should be “Lima, Peru”
capitals = [“Santiago”, “Paris”, “Copenhagen”]
countries = [“Chile”, “France”, “Denmark”]
locations = [x1 + “, “ + x2 for (x1,x2) in zip(capitals, countries)]
You’ve been given two lists: a list of names and a list of ages. Create a new list named users that contains the string “Name: name, Age: age” for each pair of elements in the original lists. For example, if the 5th item in the names list is “John”and the 5th item in ages is 42, then the 5th item in the new list should be”Name: John, Age: 42”.
As you did in the previous exercise, concatenate your strings together using +. Make sure to add proper capitalization and spaces.
names = [“Jon”, “Arya”, “Ned”]
ages = [14, 9, 35]
users = [“Name: “ + x1 + “, Age: “ + str(x2) for (x1,x2) in zip(names, ages)]
print(users)
