Combining two lists and having it repeat based on the input of the first list-CodePudding

I have these two lists of the same size:

list1 = [5, 1, 20, 19, 1, 1, 1, 1, 1] 
list2 = ['29888.20','29888.20','34298.20','35724.20','36014.20','37924.20','43886.20','54282.20', '79417.20']

The first list if you add all the indexes = 50.

5 1 20 ....

My question is I want to combine the two lists.

Where 29888.20 from the first list should be repeated 5 times from list 1 and so forth.

Another example being: 34298.20 repeat 20 times

list1[0] = 5, list2 = 29888.20 # Have list2 value repeat 5 times

Final Result should be this:

final_list = ['29888.20','29888.20','29888.20','29888.20','29888.20', # repeat 5 times
             '29888.20' # repeat 1 time
             '34298.20', '34298.20', # repeat 20 times
             '35724.20', # repeat 19 times]

           and so forth for the rest of the items in list1 and list2

I hope my explanation is making sense. help would be greatly appreciated.

CodePudding user response：

Here is a list comprehension approach with the help of zip():

list1 = [5, 1, 20, 19, 1, 1, 1, 1, 1] 
list2 = ['29888.20', '29888.20', '34298.20', '35724.20', '36014.20', '37924.20', '43886.20', '54282.20', '79417.20']

output = [j for sub in [[y]*x for x, y in zip(list1, list2)] for j in sub]

print(output)

# ['29888.20', '29888.20', '29888.20', '29888.20', '29888.20',
#  '29888.20', '34298.20', '34298.20', '34298.20', '34298.20',
#  '34298.20', '34298.20', '34298.20', '34298.20', '34298.20',
#  '34298.20', '34298.20', '34298.20', '34298.20', '34298.20',
#  '34298.20', '34298.20', '34298.20', '34298.20', '34298.20',
#  '34298.20', '35724.20', '35724.20', '35724.20', '35724.20',
#  '35724.20', '35724.20', '35724.20', '35724.20', '35724.20',
#  '35724.20', '35724.20', '35724.20', '35724.20', '35724.20',
#  '35724.20', '35724.20', '35724.20', '35724.20', '35724.20',
#  '36014.20', '37924.20', '43886.20', '54282.20', '79417.20']

For a breakdown of the list comprehension, the inner one:

[[y]*x for x, y in zip(list1, list2)]

generates a sublist containing each item in list2 repeated n times, where n is the corresponding value for list1 in the same positions. The outer list comprehension simply flattens the list of lists into a single level list of strings.

CodePudding user response：

from itertools import chain

list1 = [5, 1, 20, 19, 1, 1, 1, 1, 1]
list2 = ['29888.20','29888.20','34298.20','35724.20','36014.20','37924.20','43886.20','54282.20', '79417.20']

res = list(chain.from_iterable([[l2]*l1 for l1, l2 in zip(list1, list2)]))

output:

['29888.20', '29888.20', '29888.20', '29888.20', '29888.20', '29888.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20',
 '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20',
 '34298.20', '34298.20', '34298.20', '34298.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20',
 '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20',
 '35724.20', '36014.20', '37924.20', '43886.20', '54282.20', '79417.20']

CodePudding user response：

How about a bit of itertools:) Probably not the fastest, but looks interesting:

from itertools import repeat, chain

list2 = ['29888.20', '29888.20', '34298.20', '35724.20', '36014.20', '37924.20', '43886.20', '54282.20', '79417.20']
list1 = [5, 1, 20, 19, 1, 1, 1, 1, 1]
result = chain(*[list(repeat(list2[idx], elem)) for idx, elem in enumerate(list1)])

print(list(result))

Output:

[
 '29888.20', '29888.20', '29888.20', '29888.20', '29888.20', '29888.20',
 '34298.20',
 '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20',
 '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '34298.20', '35724.20',
 '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20',
 '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20', '35724.20',
 '36014.20',
 '37924.20',
 '43886.20',
 '54282.20',
 '79417.20'
 ]