如何将列表过滤为三个子列表？

Question

I have a list called transactions_clean , cleaned up from whitespace etc., look like this:

['Edith Mcbride', '$1.21', 'white', '09/15/17', 'Herbert Tran', '$7.29', 'white&blue', '09/15/17', 'Paul Clarke', '$12.52', 'white&blue', '09/15/17', 'Lucille Caldwell', '$5.13', 'white', '09/15/17', 'Eduardo George', '$20.39', 'white&yellow', '09/15/17', 'Danny Mclaughlin', '$30.82', 'purple', '09/15/17', 'Stacy Vargas', '$1.85', 'purple&yellow', '09/15/17', 'Shaun Brock', '$17.98', 'purple&yellow', '09/15/17', 'Erick Harper', '$17.41', 'blue', '09/15/17', 'Michelle Howell', '$28.59', 'blue', '09/15/17', 'Carroll Boyd', '$14.51', 'purple&blue', '09/15/17', 'Teresa Carter', '$19.64', 'white', '09/15/17', 'Jacob Kennedy', '$11.40', 'white&red', '09/15/17', 'Craig Chambers', '$8.79', 'white&blue&red', '09/15/17', 'Peggy Bell', '$8.65', 'blue', '09/15/17', 'Kenneth Cunningham', '$10.53', 'green&blue', '09/15/17', 'Marvin Morgan', '$16.49', 'green&blue&red', '09/15/17', 'Marjorie Russell', '$6.55', 'green&blue&red', '09/15/17', 'Israel Cummings', '$11.86', 'black', '09/15/17', 'June Doyle', '$22.29', 'black&yellow', '09/15/17', 'Jaime Buchanan', '$8.35', 'white&black&yellow', '09/15/17', 'Rhonda Farmer', '$2.91', 'white&black&yellow', '09/15/17', 'Darren Mckenzie', '$22.94', 'green', '09/15/17', 'Rufus Malone', '$4.70', 'green&yellow', '09/15/17', 'Hubert Miles', '$3.59', 'green&yellow&blue', '09/15/17', 'Joseph Bridges', '$5.66', 'green&yellow&purple&blue', '09/15/17', 'Sergio Murphy', '$17.51', 'black', '09/15/17', 'Audrey Ferguson', '$5.54', 'black&blue', '09/15/17', 'Edna Williams', '$17.13', 'black&blue', '09/15/17', 'Randy Fleming', '$21.13', 'black', '09/15/17', 'Elisa Hart', '$0.35', 'black&purple', '09/15/17', 'Ernesto Hunt', '$13.91', 'black&purple', '09/15/17', 'Shannon Chavez', '$19.26', 'yellow', '09/15/17', 'Sammy Cain', '$5.45', 'yellow&red', '09/15/17', 'Steven Reeves', '$5.50', 'yellow', '09/15/17', 'Ruben Jones', '$14.56', 'yellow&blue', '09/15/17', 'Essie Hansen', '$7.33', 'yellow&blue&red', '09/15/17', 'Rene Hardy', '$20.22', 'black', '09/15/17', 'Lucy Snyder', '$8.67', 'black&red', '09/15/17', 'Dallas Obrien', '$8.31', 'black&red', '09/15/17', 'Stacey Payne', '$15.70', 'white&black&red', '09/15/17', 'Tanya Cox', '$6.74', 'yellow', '09/15/17', 'Melody Moran', '$30.84', 'yellow&black', '09/15/17', 'Louise Becker', '$12.31', 'green&yellow&black', '09/15/17', 'Ryan Webster', '$2.94', 'yellow', '09/15/17', 'Justin Blake', '$22.46', 'white&yellow', '09/15/17', 'Beverly Baldwin', '$6.60', 'white&yellow&black', '09/15/17', 'Dale Brady', '$6.27', 'yellow', '09/15/17', 'Guadalupe Potter', '$21.12', 'yellow', '09/15/17', 'Desiree Butler', '$2.10', 'white', '09/15/17', 'Sonja Barnett', '$14.22', 'white&black', '09/15/17', 'Angelica Garza', '$11.60', 'white&black', '09/15/17', 'Jamie Welch', '$25.27', 'white&black&red', '09/15/17', 'Rex Hudson', '$8.26', 'purple', '09/15/17', 'Nadine Gibbs', '$30.80', 'purple&yellow', '09/15/17', 'Hannah Pratt', '$22.61', 'purple&yellow', '09/15/17', 'Gayle Richards', '$22.19', 'green&purple&yellow', '09/15/17', 'Stanley Holland', '$7.47', 'red', '09/15/17', 'Anna Dean', '$5.49', 'yellow&red', '09/15/17', 'Terrance Saunders', '$23.70', 'green&yellow&red', '09/15/17', 'Brandi Zimmerman', '$26.66', 'red', '09/15/17', 'Guadalupe Freeman', '$25.95', 'green&red', '09/15/17', 'Irving Patterson', '$19.55', 'green&white&red', '09/15/17', 'Karl Ross', '$15.68', 'white', '09/15/17', 'Brandy Cortez', '$23.57', 'white&red', '09/15/17', 'Mamie Riley', '$29.32', 'purple', '09/15/17', 'Mike Thornton', '$26.44', 'purple', '09/15/17', 'Jamie Vaughn', '$17.24', 'green', '09/15/17', 'Noah Day', '$8.49', 'green', '09/15/17', 'Josephine Keller', '$13.10', 'green', '09/15/17', 'Tracey Wolfe', '$20.39', 'red', '09/15/17', 'Ignacio Parks', '$14.70', 'white&red', '09/15/17', 'Beatrice Newman', '$22.45', 'white&purple&red', '09/15/17', 'Andre Norris', '$28.46', 'red', '09/15/17', 'Albert Lewis', '$23.89', 'black&red', '09/15/17', 'Javier Bailey', '$24.49', 'black&red', '09/15/17', 'Everett Lyons', '$1.81', 'black&red', '09/15/17', 'Abraham Maxwell', '$6.81', 'green', '09/15/17', 'Traci Craig', '$0.65', 'green&yellow', '09/15/17', 'Jeffrey Jenkins', '$26.45', 'green&yellow&blue', '09/15/17', 'Merle Wilson', '$7.69', 'purple', '09/15/17', 'Janis Franklin', '$8.74', 'purple&black', '09/15/17', 'Leonard Guerrero', '$1.86', 'yellow', '09/15/17', 'Lana Sanchez', '$14.75', 'yellow', '09/15/17', 'Donna Ball', '$28.10', 'yellow&blue', '09/15/17', 'Terrell Barber', '$9.91', 'green', '09/15/17', 'Jody Flores', '$16.34', 'green', '09/15/17', 'Daryl Herrera', '$27.57', 'white', '09/15/17', 'Miguel Mcguire', '$5.25', 'white&blue', '09/15/17', 'Rogelio Gonzalez', '$9.51', 'white&black&blue', '09/15/17', 'Lora Hammond', '$20.56', 'green', '09/15/17', 'Owen Ward', '$21.64', 'green&yellow', '09/15/17', 'Malcolm Morales', '$24.99', 'green&yellow&black', '09/15/17', 'Eric Mcdaniel', '$29.70', 'green', '09/15/17', 'Madeline Estrada', '$15.52', 'green', '09/15/17', 'Leticia Manning', '$15.70', 'green&purple', '09/15/17', 'Mario Wallace', '$12.36', 'green', '09/15/17', 'Lewis Glover', '$13.66', 'green&white', '09/15/17', 'Gail Phelps', '$30.52', 'green&white&blue', '09/15/17', 'Myrtle Morris', '$22.66', 'green&white&blue', '09/15/17']

These are transactions: name, cost, product, date. My job is to create three list (customer, sales, thread_sold (that's the color)) and filter the given list into these three. So the names only to the customer's list, the cost only into the sales's list and the product into the thread_sold's list. I don't need the date.

I made a code like this:

customers = []
sales = []
thread_sold = []


for item in transactions_clean:
  customers.append(item[0])
  sales.append(item[1])
  thread_sold.append(item[2])

print(sales)

I thought indexing the items in order would help, but it didn't work out. Also I don't know how to skip the dates.

Answer 1

You can solve your problem with one line of code:

customers, sales, thread_sold = [transactions_clean[i::4] for i in range(3)]

The list comprehension creates a list with three elements; each element is a list created from transactions_clean , starting at the i-th element and taking only an element every 4. In this way, when i=0 you get only the names, with i=1 only the prices and with i=2 only the colors.

Then the list created by the list comprehension is unpacked into the three required lists.

Answer 2

You can use slices for that, assuming the order in the list is consistent. Slices work like this: from:to:step_size

end_idx = len(transactions_clean)    
customers = transactions_clean[0:end_idx:4]
sales = transactions_clean[1:end_idx:4]
thread_sold = transactions_clean[2:end_idx:4]

Just saw Mr. T's comment, you can leave out the end_idx:

customers = transactions_clean[0::4]
sales = transactions_clean[1::4]
thread_sold = transactions_clean[2::4]

Answer 3

When you iterate over your list by for item in transactions_clean: you get items for each list, so indexing them like item[1] would just give you string characters. If the order is always like customer -> sale -> thread_sold, you can do something like this:

customers = []
sales = []
thread_sold = []
for i in range(len(transactions_clean) // 3):
    customers.append(transactions_clean[i])
    sales.append(transactions_clean[i + 1])
    thread_sold.append(transactions_clean[i + 2])
    

Answer 4

Modifying your code:

customers = []
sales = []
thread_sold = []


for i, item in enumerate(transactions_clean):
    if i % 4 == 0:
        customers.append(item)
    elif i % 4 == 1:
        sales.append(item)
    elif i % 4 == 2:
        thread_sold.append(item)
    else:
        continue

print(sales)

This should generate your desired lists!

Answer 5

The simplest option I see is to use the list index and iterate with the step parameter of the range iterator to get the items 4 by 4:

for i in range(0, len(transactions_clean), 4):
  customers.append(transactions_clean[i])
  sales.append(transactions_clean[i+1])
  thread_sold.append(transactions_clean[i+2])

Here, 4 is the step , so values of i will go: 0, 4, 8...